The study was conducted by scientists at the University of Pretoria (UP) in 2019 and 2020 into the prevalence of Listeria monocytogenes in beef and beef products at abattoirs and retailers in the Gauteng, Mpumalanga and North West provinces.

It showed that 4.6 percent of chilled carcasses sampled at seven abattoirs in Gauteng were positive for Listeria. This means that contaminated items could enter the food chain as beef products sold at retail outlets in the province. 

The study, funded by Red Meat Research and Development South Africa, was prompted by the 2017-2018 outbreak of listeriosis with 1,065 confirmed cases and 218 deaths. It was traced to a ready-to-eat processed meat product called polony, made at a plant in Polokwane run by Enterprise Foods, which at that time was owned by Tiger Brands.

Ready-to-eat (RTE) food, including polony, were also positive for Listeria in the current study.

Supply chain assessment
“Processed foods become contaminated by contact with equipment, the handling of raw products, or from post-processing settings in which the pathogen can survive despite the routine use of disinfectants. Because of potential contamination during slaughter, carcasses can become contaminated, leading to contaminated meat and meat products,” said Dr Rebone Moerane, head of UP’s Department of Production Animal Studies, who was part of the research team.

Another study, published in the Journal of Food Safety, revealed that 8.3 percent, or 33 of 400, beef and beef products were contaminated with Listeria monocytogenes.

University of Pretoria researchers also looked at the prevalence and factors associated with Listeria in cattle, silage, feeds, and water on farms in the three provinces; in slaughtered cattle and carcasses at processing plants; and the contamination of beef products at retail. 

Samples were collected from cattle farms; carcass swabs were taken from abattoirs, and samples of raw beef and beef products, including ready-to-eat items, were collected from shops of all sizes. 

Researchers found the risk of exposure of cattle to listeriosis on farms is minimal. However, the detection of contaminated chilled carcasses sampled at Gauteng abattoirs is troubling, as are the findings at retail outlets, they said.

Get ahead of another outbreak
The prevalence of Listeria was 6 percent, 8.3 percent, and 9.3 percent in beef and beef products sampled in outlets in North West, Mpumalanga, and Gauteng respectively, and 4.3 percent, 11 percent and 9.3 percent for cold beef and beef products.

“Some of the contaminated products were RTE items – including polony, which is widely consumed, and biltong. This increases the risk of human exposure to the pathogen,” said Dr. Moerane. 

“It’s our hope that government and industry stakeholders will act on these findings and introduce strict control and monitoring measures at the appropriate stages in the beef production system. It’s vital that we use the outcomes of this study to get ahead of another potential outbreak of listeriosis.”

In most cases, Listeria monocytogenes isolates responded to penicillin, ampicillin and sulfamethoxazole-trimethoprim, which are important antimicrobials used to treat listeriosis.

Scientists recommended that government and industry implement stringent food safety measures at abattoirs and processing plants to reduce contamination and lower the possibility of another listeriosis outbreak. 

They also suggested follow-up studies of moist biltong, which is widely consumed in the country, to determine its ability to support the growth of Listeria and assess the risk posed to consumers. 

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Nineteen sick people are aged 63 to 93, including 13 men and six women. Patients have been reported from 10 different regions.

Six people with listeriosis have died. However, it is unclear what role the infection played in their death because most patients had other severe underlying diseases.

People have been sick with the same type of Listeria since autumn 2022, but 15 cases occurred from the end of May this year, said Folkhälsomyndigheten (the Public Health Agency of Sweden).

Of cases with available information, 14 reported eating vacuum-packed salmon from one of two brands before falling sick. Both these brands are produced by Leröy Seafood, and Listeria was detected in products and environmental samples in the firm’s facility.

In most cases, samples have only been analyzed qualitatively so it is unclear if Listeria was above the limit of 100 CFU/g, according to Livsmedelsverket (the Swedish Food Agency).

“For Leröy Smögen Seafood, safe and secure food is our priority, and we take this incident very seriously. We are doing everything we can to ensure this does not happen again. We have a good cooperation and dialogue with the Swedish Food Agency,” said a company statement.

Finding the source of infections
Further analysis of samples from food, the environment, and human cases found the same type of Listeria, which points to the salmon products being the likely source of infection. The company has increased sampling and is carrying out further clean-up measures at the facility.

In early August, the retailer Axfood recalled a batch of Falkenberg Seafood cold smoked salmon 200-grams after low levels of Listeria were found.

The product was available for sale in the majority of Axfood’s stores. Listeria was detected during the retailer’s internal checks.

“The production has not been stopped, but all batches are currently analyzed for the presence of Listeria before release on the market. The company must take action following its HACCP-based procedures. They must also investigate the cause of contaminated products with Listeria monocytogenes and take measures to prevent such contamination. This may involve changes to HACCP-based procedures or other measures,” said Mats Lindblad from Livsmedelsverket.

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The Washington State Health Department reports that between February 27 and July 22, 2023, six Washington State residents (five from Pierce County and one from Thurston County) developed severe illness due to Listeria bacteria (listeriosis) infection.

All six people had conditions that made their immune systems less able to fight disease. Three of the individuals died. Genetic fingerprinting (whole genome sequencing) of the bacteria indicated that the same food was likely responsible for making all six people sick.

The restaurant discontinued the use of its two milkshake machines on August 8. The milkshake machines will be kept out of service until the Tacoma-Pierce County Health Department determines they are free of Listeria contamination and no longer pose a danger to the public.

Because milkshakes and ice cream have caused listeria outbreaks, the Tacoma-Pierce County Health Department collected milkshake samples from the restaurant on August 8, 2023. On August 18, 2023, all flavors of the milkshakes were found to be contaminated with the same strain of Listeria that caused the outbreak.

Two people infected with listeriosis reported consuming milkshakes from Frugals restaurant at 10727 Pacific Ave: S., Tacoma, WA, 98444, before becoming sick.

Also, anyone who has eaten recalled products should monitor themselves for symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

The state Department of Health is working with Pierce and Thurston County local health jurisdictions to gather information from interviews with patients and their families to help identify any common exposures.

About Listeria infections

Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause severe and sometimes life-threatening infections. Anyone who has eaten any recalled product and developed symptoms of Listeria infection should seek medical treatment and tell their doctors about possible Listeria exposure.

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Listeria bacteria are found in the environment and can spread from contaminated food to surfaces. Listeria can grow on foods kept in the refrigerator for several days. The bacteria are easily killed by heating food to a high temperature (165°F).

Although healthy, non-pregnant individuals may suffer only short-term symptoms such as fever, muscle aches, nausea, abdominal pain and diarrhea, Listeria monocytogenes is especially harmful to some people:

• For pregnant womenListeria infection can cause pregnancy loss, premature birth, or life-threatening infection in the newborn.
• Listeria infection often results in hospitalization and sometimes death for people with a weakened immune system (those (who have health problems or take medicines that lower the body’s ability to fight germs and sickness).
• For people 65 years or older, Listeria infection often results in hospitalization and sometimes death.

Pregnant women, the elderly, young children, and cancer patients with weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

People who are not pregnant usually have a fever, muscle aches, and tiredness. They may also get a headache, stiff neck, confusion, loss of balance, or seizures.

Symptoms usually start within two weeks after eating food contaminated with Listeria monocytogenes but may begin as early as the same day or as late as ten weeks after exposure.

Pregnant people usually have a fever, muscle aches, and tiredness.

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In 2022, 633 Shiga toxin-producing E. coli (STEC) infections were reported, as well as eight imported cases. This includes 620 confirmed and 13 probable cases. The number rose from 426 cases in 2021.

The highest incidences in 2022 were observed in children younger than 5 years of age, being higher in girls than in boys, according to data from the National Epidemiological Surveillance Network (RENAVE).

A total of 134 hospitalizations were reported and six people developed hemolytic uremic syndrome (HUS). HUS is a severe complication associated with E. coli infections that causes kidney failure. Four of these were younger than the age of 3, one was 10 years old, and the other was an 84-year-old adult.

Three deaths were recorded: one child younger than 3 years old who had HUS, and two adults aged 65 and 93.

For imported cases, two were younger than 10 years of age, and the rest were aged between 22 and 60.

Information on serogroup causing infection was available in 80 cases of which 67 corresponded to O157. One was O107, another was O128 and 11 were recorded as non-O157.

In 2021, two outbreaks occurred with four patients and one case of HUS. In 2022, five STEC outbreaks were reported, resulting in 13 cases and two hospitalizations.

Two were foodborne: one of them, with four cases was associated with consumption of various foods in a bar. In the other outbreak, with two cases younger than 2 years old in a nursery, the suspected food was hamburgers, and E. coli O157 was identified in clinical samples from patients.

Listeria data
In 2022, 460 patients were reported, of which 450 were confirmed, nine were probable and one was imported. In 2021, 375 patients were noted with 38 deaths.

The highest incidence rates in 2022 were found in boys less than 1 year of age, followed by men more than 75 years old and girls less than 1 year of age.

Overall, 67 deaths were reported. The age group with the most fatalities were those over 84 with 20 deaths, followed by those aged 75 to 84 with 19 deaths and 65 to 74 with 16 deaths.

In 2021, two outbreaks had four cases. This past year, nine listeriosis outbreaks were reported with 20 cases and eight hospitalizations.

In three outbreaks, the mode of transmission was food consumption. In one of them, the suspected food was poultry meat, in another it was unspecified meat, and the food implicated in the third incident was unknown. The others were caused by mother to baby transmission.

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Robert Koch Institute (RKI) scientists assigned 11 notified listeriosis patients to the incident. Despite the risk of Listeria from smoked or graved salmon being known for some time, data shows contamination still exists in production facilities and outbreaks are ongoing with further cases expected, said scientists.

Five people fell ill in 2019, one in 2021, three in 2022 and two in 2023. Five men and six women were affected, aged between 69 and 91 with a median of 79 years old.

One person who was positive for Listeria infection was reported as deceased because of causes other than listeriosis.

A Rapid Alert System for Food and Feed (RASFF) alert identified Listeria monocytogenes in smoked salmon from Poland.

“A RASFF-notification was issued because of an official sample of the mentioned product originating from Poland. Listeria monocytogenes was isolated from that sample. The link to the cluster of human cases was made by whole genome sequencing and comparison to the sequences from isolates of human origin,” said a spokesman for the Federal Office of Consumer Protection and Food Safety (BVL).

Broader problem
The specific sequence cluster type that caused the outbreak was mentioned in RKI’s epidemiological bulletin earlier this year when nine cases were known about.

This was part of wider work that identified 24 outbreaks of listeriosis across federal states with links to smoked or graved salmon products as the cause since 2010.

RKI and the Federal Institute for Risk Assessment (BfR) said measures taken so far don’t seem to be enough to protect consumers.

“The fact that cases continue to occur for many outbreaks, although possible fish products and manufacturers have been identified, casts doubt on the efficiency of measures taken and strategies pursued to minimize Listeria contamination,” they added.

People at an increased risk of listeriosis should only eat fish and seafood that have been well cooked. Smoked and graved salmon products should not be offered to vulnerable groups, such as immunocompromised people and the elderly in healthcare facilities, said the BfR.

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The incidence of invasive listeriosis in Finland is higher than the EU average, and most cases are in the elderly with a pre-existing condition, according to the study published in the journal Epidemiology and Infection.

Eating high-risk foods
From 2011 to 2021, 722 listeriosis cases were reported, ranging from 42 to 93 per year. The median age of patients was 75 but ranged from 8 to 101 years old, and the incidence rate was 11-fold in those older than 75 compared to other age groups.

Most interviewed patients in the study were immunocompromised because of an underlying illness or medication use. Interview data were obtained for 304 cases from 2016 to 2021. For patients with underlying diseases, the main ones were heart disease, diabetes, other cancers than leukemia, lung disease, and chronic kidney disease.

In Finland, whole genome sequencing (WGS) was introduced in 2015 for Listeria confirmation and typing, and interviews of listeriosis cases were launched in 2016 at the Finnish Institute for Health and Welfare (THL). Since starting interviews with patients, eight outbreaks with 133 patients could be solved with both epidemiological and microbiological evidence. They were linked to fish products, fresh or frozen vegetables, and meat and lasted for between three and seven years.

Two weeks before the start of symptoms, 71 of 297 had been in inpatient treatment, 84 of 294 had eaten in a restaurant, 38 of 285 had traveled in Finland, and 14 of 283 had been abroad. The most consumed risk foods recorded were ready-to-eat meat cold cuts and cured and cold- or hot-smoked fish. Many patients had high-risk foods or reported improper food storage.

In Finland, listeriosis in pregnant women is rare. They are advised to eat fish products only properly heated and to avoid sushi, roe, and foods containing raw fish. Unheated meat cold cuts are deemed safe if consumed well before the use-by date.

“This suggests that recommendations about high-risk foods and proper food storage should also be highlighted to other risk groups than pregnant women, as well as to relatives and people taking care of the elderly,” said researchers.

Of the cases, 96 of 286 reported a habit of checking their fridge’s temperature once a week, 25 said once a month, and 73 said less frequently. Also, 179 reported throwing out outdated products once a week, 29 said once a month, and 25 said less frequently. Almost 100 cases did not know of risky foods for listeriosis before infection.

Matching Listeria from patients to a food source
From 2011 to 2021, the Finnish Food Authority received 4,939 Listeria monocytogenes isolates from foods and production plants from 23 local official food control labs. Isolated strains represented 3,353 samples—more than 100 food samples contained above 100 Listeria colony-forming units (CFU)/g. 

The overall occurrence of Listeria in food products in Finland is unknown, as no national sampling surveys have been conducted since 2016.

Since 2018, the Finnish Food Authority has been typing food isolates with a similar method to that used for patient isolates, enabling comparison of Listeria strains. Researchers found matching food isolates that gave microbiological evidence to support epidemiological findings in outbreak investigations.

Researchers combined data from Finnish national listeriosis surveillance, patient interview responses, and laboratory data of patient samples. They compared them to Listeria findings from food and food production plants collected during outbreak investigations from 2011 to 2021.

Using WGS, from 2015 to 2021, scientists identified 23 clusters with five or more patient isolates, many of which persisted for years. In 12 clusters, food or environmental isolates were also detected.

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Michael Vasser, from the CDC, gave details about the reoccurring, emerging and persisting (REP) strain during a recent presentation at the International Association for Food Protection.

An REP strain is a reoccurring, emerging and persisting group of bacteria, closely related by whole genome sequencing, that continues to cause illness over time. The CDC recently reported that almost 3,000 infections from a persistent strain of Salmonella Infantis since 2012 are linked to chicken.

“Since the full transition to whole genome sequencing to detect multi-state outbreaks, at CDC we’ve been able to identify strains that continue to see cases over time. We saw an outbreak of Salmonella Newport return in 2018 after it was originally investigated in 2016 and 2017. The outbreak caused more than 400 illnesses that resulted in a very large ground beef recall,” said Vasser.

“That begs the question, had we understood the strain in 2016-17 could we have prevented such a large outbreak from occurring? We decided to collaborate with other state and federal regulatory partners to create this new concept, which is reoccurring, emerging and persisting strains.”

Vasser said approaches to investigating REPs may be different than traditional outbreak methods and about 20 REP strains are currently being monitored.

“We know that most illnesses reported through PulseNet are not linked to a source. The goal is to use REPs to drive down the incidence of illness and to better understand sporadic illness. REP strains offer a means of tracking and investigating problems that are larger in scope than traditional outbreaks but we know we need to keep pushing on translating tracking into action and prevention.”

Listeria example and potato link
Vasser gave an example of long running related Listeria infections. The PulseNet laboratory network identified a cluster of six clinical isolates in February 2017 from four states. People fell ill between May 2016 and February 2017. The same pattern was also seen in two isolates from 2011. Patients reported consumption of ice cream, so multiple production facilities were inspected and samples collected but the outbreak strain was not found.

By March 2018, there were 23 illnesses from 12 states. Open-ended interviews then suggested various frozen foods such as pizzas, meals and snacks. However, in May 2018, isolates from U.S. potatoes were uploaded to the NCBI database by the National Service of Health for Food Safety and Food Quality (SENASICA) in Mexico. Isolates were collected from fresh, raw potatoes grown in the U.S. and tested at export by Mexico.

The REP code was officially assigned in June 2021 with 66 illnesses from 21 states. Potatoes were not on the original Listeria questionnaire but now a potato specific version is being used and all 13 patients interviewed reported consuming potatoes in some form. For nine people, it was frozen potato products.

Currently, 82 cases have been reported from 23 states, with Texas the most affected. Sick people range from less than 1 to 104 years old. The latest case was in April 2023. A total of 66 have been hospitalized, 18 are pregnancy-associated and 12 have died.

“This REP is challenging given the related raw potato isolates and the enormity of items made with fresh potatoes. It is still unclear if potatoes are actually the source of infections or if contaminated potatoes seeded the strain in facilities or environments where other foods are grown or processed. It could be that both potatoes and others foods are contaminated. Sampling of products will likely be our best bet to determining the source of foods causing illness,” added Vasser. 

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The advice comes from a risk assessment by the Food Standards Agency (FSA) and Food Standards Scotland (FSS) that shows these groups are at a higher risk of severe illness from listeriosis. The risk assessment was prompted by an outbreak of Listeria infections linked to RTE cold-smoked fish.

Past advice listed smoked fish as a food of concern with the recommendation that care should be taken during pregnancy and it should only be eaten by vulnerable groups after being thoroughly cooked.

The FSA, FSS, and UK Health Security Agency (UKHSA) have been investigating the ongoing outbreak since October 2020. There have been 19 linked cases of listeriosis in England and Scotland and four people have died, this is up from the 15 cases and three deaths reported several months ago. Most patients are above 65 years old but one was a pregnant woman. 

In December 2022, Lidl recalled Deluxe Oak Smoked Scottish Louch Trout and Lighthouse Bay Smoked Trout Trimmings, produced by St James Smokehouse. Product testing found Listeria monocytogenes that matched the outbreak strain but levels were below permitted limits.

Potential for serious illness
In RTE foods that can support growth of Listeria, which include smoked fish, the bacterium must not be present in 25-grams of sample when leaving production plants, or businesses must show the products will not exceed the limit of 100 Colony Forming Units per gram (CFU/g) during their shelf life.

As the risk of serious illness from listeriosis increases with age, FSA and FSS are also advising that people older than 65 should be aware of the potential danger posed by products such as smoked salmon or trout and gravlax. Neither the cold-smoking process nor refrigeration kill Listeria.

The assessment found that while the risk of contracting listeriosis in higher-risk individuals from cold-smoked fish is low, severity of illness is high. This means there is the potential for serious illness, hospitalization, and death among higher risk groups.  

Uncertainties included the difficulty in estimating the infectious dose for Listeria monocytogenes and how it varies between different vulnerable groups; the long incubation period which can make attribution to a food vehicle difficult; the initial level of contamination and how it multiplies through the food chain; and consumer behavior around use-by dates and temperature abuse.

Professor Robin May, FSA chief scientific adviser, said: “Our risk assessment shows that there is still an ongoing risk to health associated with eating cold-smoked fish for specific groups of vulnerable people, including pregnant women and individuals with impaired immunity. In light of the risk assessment, we are advising that these consumers avoid ready-to-eat cold-smoked and cured fish products.” 

Those with weakened immune systems are people with certain underlying conditions such as cancer, diabetes or liver and kidney disease.

Fish processing details
Cold-smoked fish such as smoked salmon or trout, and cured fish such as gravlax, have not been fully cooked during the production process to kill any Listeria that may be present. Cold-smoked fish is normally labeled as smoked fish on packaging, so processing type is unclear. RTE cold-smoked fish typically comes in thin slices, and can be eaten cold. It may also be found in sushi.   

Smoked fish products that have been heat-treated during production, such as tinned smoked fish, are safe for consumption without further cooking. These products are subjected to a high temperature during processing, which is sufficient to kill Listeria.

Gauri Godbole, consultant microbiologist at UKHSA, said: “While smoked fish has a higher risk of carrying Listeria, the overall risk to the population is very low. However, some people are more likely to get a serious infection including those who are pregnant and those with weakened immune systems. The risk also increases with age. Those who are more vulnerable can be at risk of severe illness such as meningitis and life-threatening sepsis. Listeriosis in pregnancy can cause very serious illness in mothers and their babies.”

UKHSA has identified 31 patients with microbiological and epidemiological links to eight smoked fish incidents between 2015 and June 2023, with eight deaths and three pregnancy associated patients.

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Folkhälsomyndigheten (the Public Health Agency of Sweden) said deaths of three of the older patients were connected to their Listeria infections but it is not clear if they died with or because of listeriosis.

From the end of May to the beginning of July, 10 people contracted Listeria infections caused by the same type of the bacteria. Another four people fell ill in late 2022 from this strain.

Patients are 10 men and four women aged 63 to 93 years old. They live in eight different regions in the country.

Based on information from a questionnaire given to patients about foods they ate before becoming sick, many reported eating gravad or cold-smoked salmon but the exact product that caused the outbreak is not yet clear.

Warning for vulnerable groups
Folkhälsomyndigheten, Livsmedelsverket (the Swedish Food Agency) and regional infection control units are investigating the illnesses.

Livsmedelsverket said Listeria can cause serious illness for people in at-risk groups, such as pregnant women, the elderly and people with impaired immune systems.

“Those who belong to a risk group — or who are to offer food to someone in a risk group — can reduce the risk of infection by following the Swedish Food Agency’s advice on Listeria. Certain foods such as blue cheeses should be avoided completely, while other foods such as cold smoked and gravad salmon should be eaten within a week of the date on the packaging,” said Jonas Toljander, a microbiologist at Livsmedelsverket.

In 2022, 125 listeriosis cases were reported compared to 107 the year before. The median age was 79 and as in previous years, most were older than 80. Overall, 45 people died within one month of diagnosis.

National and local authorities took 266 samples from different types of food to test for the presence or absence of Listeria monocytogenes in 2022. The pathogen was detected eight times. Two of these were vacuum-packed salmon taken as part of work into a suspected food poisoning or complaint.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

Also, people should monitor themselves for food poisoning symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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The Norwegian Institute of Public Health (FHI) reported that three women and one man fell ill in June and were admitted to hospitals. All patients are now either healthy or improving.

They are between the ages of 50 and 80. Two live in Viken, and one each in Vestland and Oslo.

Listeria with the same genetic profile has been detected in samples from all patients, which indicates a common source of infection.

FHI, the Norwegian Food Safety Authority (Mattilsynet), the Veterinary Institute and relevant municipal officials are part of the investigation. The Norwegian Food Safety Authority has interviewed sick people and obtained samples, which the Veterinary Institute has analyzed.

Three out of four people reported having eaten either smoked salmon or smoked trout from Troll Salmon in the period before they became ill. The outbreak strain was found in two packs of smoked salmon from this company. One person had the packages in the freezer.

In July, Troll Salmon recalled smoked salmon with lot number 216 and a date of May 23.

Similar problem in 2022
The strain in this incident is also similar to the one detected in an outbreak of listeriosis in 2022 where smoked salmon was the suspected source of infection.

From April to October 2022, the Norwegian Institute of Public Health detected listeriosis in five people. Sample dates ranged from February to October.

Cases were two women and three men aged 50 to 95 with a median of 72 years old. They lived in four counties: Nordland, Trøndelag, Viken, and Oslo, and all were hospitalized.

“The Norwegian Food Safety Authority is in close dialogue with the business, which must ensure that they do not sell products that represent a possible health hazard for consumers. The Norwegian Food Safety Authority also monitors that the company carries out necessary investigations and implements sufficient measures in production,” said Lindis Folkvord, from Mattilsynet.

At an inspection in October 2022, the Norwegian Food Safety Authority discovered the fish producer’s sampling plan was not sufficient, and that environmental samples had not been taken in line with Troll Salmon’s internal program.

The firm was ordered to take daily samples for a certain time period and to update the sampling plan. It also carried out additional cleaning and disinfection of premises and equipment.

Listeria had been found in two smoked salmon products from the company earlier in 2022, but at a concentration below the legal limit, so they were not recalled. Samples were taken during the monitoring of ready-to-eat food in shops, a program under the Norwegian Food Safety Authority.

During the inspection, Listeria monocytogenes was found in environmental samples from the producer. However, these isolates had a different profile to the outbreak strain but were similar to those taken from the firm’s smoked salmon in the monitoring work.

In 2022, Norway had two Listeria outbreaks with 10 people sick. Infections went up from 20 in 2021 to 31 in 2022. Of these, 27 were infected in Norway and four were infected abroad. All patients were hospitalized. 

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They still remember, and each Aug.23, Maple Leaf Foods recognizes those sickened and those who died in Canada’s 2008 listeriosis outbreak.

Cold cuts from a Maple Leaf Foods plant in Toronto were the source of that deadly outbreak that was known for killing elderly Canadians across several provinces.

The deadliest food-borne disease outbreak in Canadian history resulted in a six- to eight-week product shortage when Maple Leaf shut down operations.

It is no surprise that the International Association for Food Protection, at its annual meeting being held in Toronto this week, would address the historic event. The session titled: “Foodborne Listeriosis in Canada, Are we there yet?” covered most of the bases. “Insights into Progress and Lessons Learned Since Our Infamous Deli-Meat Outbreak,” added if a subtitle was needed.

Heath Canada’s Marie Breton was the panel’s lead-off speaker, providing an in-depth look at her country’s past and future policies for controlling Listeria. She showed how two-thirds of Canada’s listeria policies that were in place by 2011 were in existence by 2008, the year when the listeriosis tragedy occurred.

Lynn McMullen from the University of Alberta at Edmonton said, “One size does not fit all” when considering Listeria and that researchers must consider both the transient and persistence of the pathogen’s strains.

In illustrating how difficult persistent Listeria can be, McMullens showed how Listeria remained in the cheese plant for some seven years. She pointed to the need for improved sanitation practices because of evidence that current procedures “are not enough.”

After the regulatory and research presentations, Randy Huffman from Maple Leaf Foods appeared to tell how the company became an adherent to a food safety culture in response to the deadly outbreak. He credits the company’s former chairman, who from the outset assured Canada their food safety system was among the world’s best. He also said Canada’s regulators were not to blame, just Maple Leaf Foods.

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The large listeriosis outbreak with 55 cases affected Germany, Austria, Denmark, and Switzerland during 2020 and 2021. Three people died.

Investigations of food samples identified Listeria monocytogenes from smoked rainbow trout filets from Agustson, a Danish producer, grouping with isolates from cases. Patient interviews confirmed the consumption of rainbow trout as the likely infection source. 

The outbreak was identified by molecular surveillance in Germany. Routine whole genome sequencing (WGS) of clinical Listeria monocytogenes isolates was implemented in the country in 2018. 

Details of people sick
In November 2020, a sudden increase in related isolates was detected. Information on the cluster was shared via the Epidemic Intelligence Information System (EPIS) platform of the European Centre for Disease Prevention and Control (ECDC) in the same month.

This returned two recent closely related isolates in both Austria and Denmark and one in Switzerland, indicating the possible cross-border distribution of a contaminated food item.

In total, 68 isolates were recorded between September 2020 and January 2022 in the four affected countries with 63 in Germany. The last isolate was collected on Jan. 31, 2022, according to the study published in the journal Microbiology Spectrum.

Overall, 55 notified cases could be allocated to the outbreak isolates. They were reported from October 2020 to January 2022 with the majority from mid-October to mid-November 2020. Seven cases were reported later in 2021, and one was reported in January 2022.

Of these cases, 50 were from Germany, two each from Austria and Denmark, and one from Switzerland.

Of German patients, 22 were female, and their median age was 80 with a range from less than 1 to 94 years old. Three people died but for one case, another cause of death was notified, and for two people, the cause was not reported. Two cases were pregnancy-associated.

The outbreak had a sudden and marked increase in case numbers and was of a comparably short duration. Other listeriosis outbreaks in Germany are normally active for years before they are detected and stopped.

Researchers interviewed 19 of the 55 cases about food consumption prior to disease onset, and 16 recalled having eaten smoked trout. It was the most frequently reported food item from the standardized questionnaire in Germany, followed by Gouda cheese.

Search for source
A matching food isolate was detected inside an emptied and reclosed package of smoked rainbow trout filets from the waste bin of a patient in Germany. The product was manufactured by Agustson in Denmark.

In December 2020, the Rapid Alert System for Food and Feed (RASFF) warned of Listeria monocytogenes in another batch of smoked rainbow trout filets of this brand in an official sample taken in October, which exceeded the limit for Listeria ready-to-eat products. At the time of the notification, the affected batch had already expired. This isolate was also similar to samples from patients.

The same brand of smoked trout was sold in supermarkets in the four countries where listeriosis cases were identified. Altogether, this strongly indicates the outbreak was caused by rainbow trout filets from the Danish producer, said scientists.

A recall was issued in December 2020 and investigations at the processing facility in Denmark identified Listeria monocytogenes, but the isolate did not belong to the outbreak cluster. Hygiene and disinfection measures at the plant were intensified.

“Our report demonstrates that international food trade can cause multi-country outbreaks that necessitate cross-border outbreak collaboration. It also corroborates the relevance of ready-to-eat smoked fish products as causes for listeriosis,” said scientists.

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In 2021 and 2022, there were 66 cases of listeriosis in 15 outbreaks, reported the Robert Koch Institute (RKI).

A total of 24 outbreaks of listeriosis across federal states with links to smoked or graved salmon products as the cause have been found since 2010.

This is an update from a previous study that identified 22 outbreaks between 2010 and 2021 that were associated with eating smoked and graved salmon products. Many also affected people in other countries. 

Severe underreporting is to be expected for listeriosis outbreaks, so it can be assumed that the number of cases in Germany is significantly higher, said scientists.

Updated figures
In 2021 and 2022, closely related isolates continued to be identified in smoked or graved salmon products for 11 of 22 outbreaks from 2010. For one of the two new outbreaks, related food isolates were reported in Denmark.

In 2021, 29 people were sick in 12 outbreaks and in 2022 there were 37 cases in 11 outbreaks. Another 19 cases fell ill before 2021 and were identified retrospectively.

Overall, the data includes almost 300 patients from 2010. The largest outbreak involves 41 cases.

Listeriosis cases in 2021 and 2022 were 17 to 95 years old with a median age of 78. A total of 39 males and 27 females were affected. Nine deaths were reported to the RKI and four died directly or indirectly from listeriosis. This takes the total to 57 deaths from 2010, with 21 linked to Listeria infections.

One illness associated with pregnancy was reported, bringing the total to five from 2010 to 2022.

Multi-year and international incidents
Despite the risk of Listeria from smoked or graved salmon being known for some time, 2022 data shows contamination still exists in production facilities and outbreaks are ongoing with further cases expected, said scientists.

RKI and the Federal Institute for Risk Assessment (BfR) have not yet been able to find in what companies and at which processing steps contamination occurs. The agencies said any measures already taken don’t seem to be enough to protect consumers.

The fact that cases continue to occur for many outbreaks, although possible fish products and manufacturers have been identified, casts doubt on the efficiency of measures taken and strategies pursued to minimize Listeria contamination, said RKI and BfR.

Communication by RKI via the EpiPulse system of the European Center for Disease Prevention and Control (ECDC) found cases in other EU countries or the United Kingdom for two more outbreaks, taking the total to 13 international events. The similarity of isolates makes it likely that sources of infection are the same, said scientists.

A total of 259 non-clinical isolates from fish products and fish-associated production environments in Germany showed a close relationship to 23 listeriosis clusters. Most isolates came from smoked or graved salmon products.

In 2021 and 2022, 25 cases of listeriosis or their relatives were asked about food consumption and shopping behavior. Of these, 16 said they had consumed smoked salmon or smoked fish in the two weeks before the onset of the illness.

Food safety and infection control measures are increasingly necessary to minimize the risk of listeriosis from smoked or graved salmon. Risk communication and risk management are needed in Germany and at the international level to stop contamination of these products with Listeria and also the outbreaks said scientists.

People at an increased risk of listeriosis should only eat fish and seafood that have been well-cooked. Smoked and graved salmon products should not be offered to vulnerable groups, such as immunocompromised people and the elderly in healthcare facilities, said the BfR.

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Whole genome sequencing of listeriosis samples by the UK Health Security Agency (UKHSA) has identified three cases with one death, possibly as part of an outbreak.

Patients are aged 59 or older and are from the south of England or London. One person fell sick in November 2022, while the other two became ill in February 2023.

A similar strain as the one from patient samples has also been found in some unspecified food products and samples taken from food production environments.

The Food Standards Agency (FSA) has warned people not to eat Baronet soft cheeses because they are contaminated with Listeria. In some cases, an “exceptionally high” level of the pathogen was found.

A closely genetically related strain of Listeria monocytogenes found in samples of Baronet cheese was detected in the three patients. Epidemiological investigations are continuing.

Product recall
The Old Cheese Room has recalled Baronet, Baby Baronet, and Mini Baronet Soft Cheese because of Listeria monocytogenes. Baronet is a pasteurized semi-soft cheese with a pinkish-orange rind and a pungent smell. Different pack sizes and best-before dates are affected with dates up to April 18. The latest list can be found here.

Cheese can be served sliced from deli counters. Consumers have been advised to contact the retailer they bought their Baronet cheese from to see if what they purchased was from the businesses and batches covered in the recall.

“Due to this outbreak of Listeria monocytogenes, we are urging consumers who are vulnerable to Listeria infection – including people who are pregnant and people with weakened immune systems to ensure they follow the advice in the product recall notices, which detail all of the products which may pose a risk,” said Tina Potter, FSA head of incidents.

“We are also asking people to make sure that elderly relatives who may have purchased the recalled items, and who are at particular risk, are aware of the recall and observe the advice.”

Old Cheese Room’s Response
Businesses are being advised to check whether they have been impacted by product withdrawal and recalls. If suppliers have sold onto retailers, it is vital that each retailer carries out a recall and informs their local authority, said FSA.

Any companies that have received affected products need to ensure good hygiene to prevent the risk of cross-contamination. It is possible that other cheese, if handled using the same equipment or on common surfaces, may also become contaminated, added the agency.

The Old Cheese Room said a batch that was originally tested by environmental health officers during an annual visit and that came back clear, was found to be positive for Listeria as part of retesting.

No Baronet of any size has been made since the start of March.

“We have not been told not to make Baronet by any authorities, however, it seems a sensible decision not to make any until we have found the source of the issue. As responsible cheesemakers we carry out regular cleaning, disinfecting, and swab testing of our making and ripening rooms. We have now changed our monthly testing regime to positive release, this means that we test every batch of cheese before it leaves our premises,” said a company representative.

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The awareness campaign was a risk communication strategy aimed at reducing Listeria. However, the study showed the prevalence of Listeria monocytogenes in high-risk RTE facilities was largely unchanged between 2016 and 2020. Also, cases of listeriosis went up from 39 in 2016 to 86 in 2022.

To assess the presence and persistence of Listeria monocytogenes in Danish ready-to-eat (RTE) food companies in response to a Listeria awareness campaign, the production environment of selected fish and meat firms was sampled in 2016 and 2020.

After a listeriosis outbreak that involved 41 cases and 17 deaths in 2014 caused by a contaminated RTE spiced meat roll product, the Danish Veterinary and Food Administration (Foedevarestyrelsen) launched a Listeria awareness campaign in 2015–2016 with information and educational activities aimed at producers of high-risk products, food inspectors and the public.

The number of companies that tested positive for culture was 17 out of 39 in 2016 and 11 out of 34 in 2020, indicating a limited effect of the campaign, found the study published in the MDPI journal Hygiene.

Limited success and more infections
A total of 777 environmental samples were obtained from 53 companies, of which 32 and 20 samples were positive for Listeria monocytogenes in 2016 and 2020, respectively. Four companies tested positive in both years. 

Only 20 companies participated in both years and the number of samples per firm varied. Also, testing in 2020 was focused on the area after heat treatment rather than where raw materials were handled.

Whole genome sequencing (WGS) characterized 50 isolates from 24 companies, plus another 35 from routine surveillance from 2016 to 2020.

Ten different sequence types had been implicated in cases in Denmark during the study period and five of them were also found in the food companies. Analysis of one strain suggested it had persisted over time in the production environment and may have caused human cases, with a 6-year interval.

Results showed the same sequence types can be isolated over long periods from the same companies. Isolates belonging to the same sequence type and from the same companies were genetically similar regardless of year or whether samples were from products or the environment, indicating the persistence of some sequence types.

“Prevalence of Listeria monocytogenes remained comparable between 2016 and 2020 samplings, which, taken together with the increasing trend in listeriosis cases in Denmark, may indicate that the current risk communication strategy is not working, despite the DVFA’s intensive Listeria awareness campaign and availability of comprehensive information on the agency’s website,” said scientists.

Listeria in Germany
Meanwhile, another study has looked for Listeria at fruit and vegetable producers in Germany.

From July 2020 to June 2021 in Bavaria, 39 producers of soft fruit, vegetables, and ready-to-eat raw fruits and vegetables were checked. Inspections were at the farm, primary production, and processing stages.

Environmental and food sampling as well as testing of irrigation and processing water was performed to investigate the prevalence of Listeria species including Listeria monocytogenes.

A total of 407 samples were taken including 229 swab samples from food contact materials and the environment, 59 food samples, and 119 samples of irrigation and processing water.

In 51 samples, Listeria spp. was detected. Listeria seeligeri was the most identified species, followed by Listeria innocua, Listeria monocytogenes, and Listeria ivanovii, according to the study published in the Journal of Food Protection.

Listeria monocytogenes findings
Listeria monocytogenes were identified in seven environmental and processing water samples but not in food. These isolates were detected in six different facilities, three at the primary production level, and four at processing plants.

The common isolation area of Listeria monocytogenes was the facility surroundings, especially in different gullies and drains. One processing water sample of a lettuce washing system was positive at the primary production level.

Listeria monocytogenes were found in a drain where ready-to-eat salad with products of animal origin (POAO) were processed, highlighting the need to comply with good manufacturing and hygienic practices, especially when both types of products are processed at the same premises.

Swab samples showed the highest prevalence of Listeria. Irrigation and processing of water and food samples had a lower prevalence. More than one type of Listeria was found in 12 samples.

The detection of different Listeria species within the same company suggests the pathogen may become an issue if hygienic environmental handling is neglected, said researchers.

“In addition to water sources and quality, this study demonstrates that irrigation regime, cultivation, hygienic handling, and maintenance protocols are highly important to reduce the potential contamination of ready-to-eat soft fruits and vegetables with Listeria,” they added.

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The five cases of listeriosis include four pregnant women who gave birth prematurely. They were infected with the same type of Listeria and reported symptoms between April and December 2022. No related deaths have been reported.

Health officials said that patients had consumed products sold under the Jay & Joy brand in the weeks before their illness. The firm makes cheese alternatives from almond milk and organic cashew nuts.

Santé Publique France, the National Reference Center (CNR) Listeria, the Directorate General for Food (DGAL), the Directorate General for Competition, Consumption and the Repression of Fraud (DGCCRF), and the General Directorate of Health (DGS) are involved in the outbreak investigation.

Control measures and recall
An inspection has revealed “irregularities” at the company, especially around controls to manage the microbiological contamination risk of products made in the factory. Authorities have suspended the marketing of all products stored and manufactured at the site. Epidemiological and microbiological investigations are ongoing.

Jay & Joy has issued a withdrawal and recall notice for all products with dates between Jan. 14 and March 30, 2023. Distributors include Biocoop, Naturalia, Relais Vert, Vita Frais, Natureco, and Effegi. People were asked by officials not to consume these products and to return items to the place of sale.

Distribution of affected products also includes Austria, Belgium, Germany, Ireland, Italy, the Netherlands, Singapore, Spain, Switzerland, and the United Kingdom, according to a notification on the EU’s Rapid Alert System for Food and Feed (RASFF) platform. 

Three additional cases have been identified in Germany, Belgium and the Netherlands. People were questioned by national health authorities in these countries and confirmed consumption of Jay & Joy products.

The company recalled a product in France in April 2022 because of Listeria. In July, Jay & Joy issued a recall in France, Belgium, Germany, and the Netherlands due to potential Listeria contamination, and another recall for Listeria was made in August in Belgium.

About Listeria
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has eaten any recalled product and developed symptoms of Listeria infection should seek medical treatment and tell their doctors about possible Listeria exposure.

Also, anyone who has eaten any of the recalled products should monitor themselves for food poisoning symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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The Federal Office of Public Health (OFSP), Federal Food Safety and Veterinary Office (OSAV), and cantonal, or regional, authorities detected an outbreak of listeriosis in July 2022 and identified smoked trout as the source.

In early July, an unusually high number of Listeria monocytogenes cases were reported to OFSP. Whole genome sequencing (WGS) confirmed they were linked.

As part of an investigation carried out with OFSP, patients were interviewed and evidence pointed to smoked trout produced by one company.

Cantonal food authorities carried out an inspection of the firm in the canton of Thurgovie, also known as Thurgau, which found the bacteria in smoked trout and in the production environment. WGS matched the isolates from food samples and patients, confirming the link.

In July, smoked fish from the company Kundelfingerhof was withdrawn from sale and recalled from stores such as Coop, Migros, and Volg.

Of the 20 people affected, 10 were men and 10 were women. They were between 58 and 89 years old but half of them were older than 75. The first two cases were in April 2022 but the majority were reported in June and July.

Zurich was the canton with the most infections with nine while 18 patients came from the northeast of the country. Nineteen people were hospitalized and one person died.

Production stopped and improvements made
During patient interviews, 17 people mentioned eating fish before falling sick, 11 had consumed meat products, 15 had eaten smoked trout and a dozen people mentioned the same company.

In mid-July, OFSP informed OSAV about the outbreak, who passed information to the cantonal laboratory of Thurgovie, which then checked Kundelfingerhof. Listeria was detected from various product samples. They were later found to match those from patients in the outbreak.

Products were recalled, OSAV issued a public warning, and production was temporarily stopped. Authorities said the cause of the contamination was determined and eliminated. Kundelfingerhof has since adapted its self-checking measures and restarted production.

Kundelfingerhof reported the financial impact was more than a quarter of a million Swiss francs (around $271,000), which was higher than first estimated but part of it was covered by insurance.

Operations at the fish smokehouse were halted for about two months but the all-clear was given in September 2022 after measures that included lab testing.

With the involvement of external experts, structural changes were made, the fish processing site was cleaned and decontaminated plus monitoring was intensified.

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AKV, an association to protect creditor rights recognized by Austrian authorities, deals with insolvency cases in courts.

It reported that Käserei Gloggnitz can no longer meet its payment obligations. Insolvency proceedings have been opened by the regional court in Wiener Neustadt. A hearing is planned for early February 2023.

The reasons for the insolvency position are unknown, according to AKV. So the impact of the Listeria monocytogenes incident on the company is unclear.

As part of the proceedings, it will have to be checked whether the dairy producer will be continued and restructured or if existing assets will be inventoried and valued.

Outbreak and recall details
Insolvency proceedings around the assets of the company were already pending at the regional court but a restructuring plan was unable to be fully implemented.

The Austrian Agency for Health and Food Safety (AGES) found 10 infections since 2020 because of an identical Listeria strain. Three people died between 2020 and 2022. Illnesses occurred in Vienna. Patients were six women and three men between 29 and 82 years old plus a newborn baby.

Käserei Gloggnitz recalled all kajmak, drinking yogurt, and cream cheese products in September because of potential Listeria monocytogenes contamination. Kajmak is a type of cheese.

Officials found Listeria that matched the outbreak strain in three environmental samples taken from the company in Lower Austria. The outbreak strain was also detected in the food it produced. Items were used in a restaurant, which was mentioned in patient interviews.

Wiener Neustadt’s public prosecutor’s office is also still investigating the incident.

In a different Listeria outbreak in Austria, revealed in mid-December, four people are sick. Chilled smoked mackerel from the Czech Republic is being looked at as a potential source. An AGES spokesman said as food authorities were still investigating the incident, the agency could not provide any further information.

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Salad and other fresh produce were collected in England from retail and catering businesses from September 2020 to December 2021 and were tested for Salmonella, Shiga toxin-producing E. coli (STEC), Listeria, Bacillus cereus, and E. coli.

From more than 600 samples, 84 percent were judged satisfactory, 12 percent were borderline, and 4 percent were unsatisfactory, found the study just published in the Journal of Food Protection.

Results do not suggest an improvement in microbiological quality since studies over the past 20 to 25 years, said researchers.

Sampled products included salad leaves, tomatoes, fresh herbs, cucumber, carrot, pepper, onion, and cabbage. The majority of items with a known origin were from the UK or Europe. 

STEC and Listeria findings
A sample of prepacked leaves, cucumber, and tomato from a caterer was unacceptable because STEC O76 was detected but no human infections in the United Kingdom matched this isolate. A sampling of the same salad product from the same premises four weeks later found no STEC.

No Salmonella was detected, but Listeria monocytogenes was recovered from 11 samples. Bacillus cereus was at borderline levels in 9 percent of samples and at an unsatisfactory level in one sample. E. coli was found in 3 percent of samples at borderline levels and in 4 percent at unsatisfactory levels.

One Listeria isolate matched human cases and was from a prepacked mixed salad from a catering business in 2021. It was the same strain that was behind a multi-country outbreak from 2015 to 2018 associated with frozen sweetcorn produced in Hungary by Greenyard but no link in the supply chain was established. There was no information on countries of origin for components in the salad product tested in 2021. A dozen people were sick in the UK from 2015 to 2021.

The strain that clustered with isolates from the outbreak of listeriosis was recovered from a bag of bistro salad containing lettuce and beetroot collected from a catering site that had purchased it from a national supermarket chain in August 2021. Despite a recall in 2018, the outbreak strain was detected in England at the importer in 2019, in a patient in 2019, and in another sick person in 2020.  

Listeria species other than Listeria monocytogenes were detected in 19 samples. One sample was contaminated at borderline levels of 100 Colony Forming Units per gram (CFU/g) with Listeria innocua, and another with Listeria monocytogenes was also positive for Listeria seeligeri. Among the 11 samples in which Listeria monocytogenes was detected, five were recovered from loose products taken from two premises.

COVID-19 impact
Elevated levels of E. coli were mostly in loose products from the UK from caterers in the summer or autumn of 2021 and may have resulted from the relaxation of COVID-19 restrictions, said, scientists. 

The study showed 1.7 percent contamination with Listeria monocytogenes and 4 percent with E. coli at levels above 100 CFU/g.

Higher levels of Bacillus cereus occurred in a range of salad types and were in similar proportions among loose and prepacked products, as well as in samples from catering and retail settings and different countries of origin.

An association was observed between E. coli and Listeria in salad products. Cross-contamination and poor hygiene in catering environments are likely to be major factors, said researchers.

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Food Standards Scotland (FSS) and the Food Standards Agency (FSA) have now named the company involved in the outbreak that has affected 15 people since October 2020 in England, Scotland, and Wales. Nine patients have become ill since January 2022, with many of them eating ready-to-eat smoked fish before falling sick.

Most patients are above 65 years old but one was a pregnant woman. Three people older than 65 have died and for two Listeria monocytogenes was a contributory cause of death. All cases had underlying health conditions.

Products positive at low levels
Lidl GB recalled Deluxe Oak Smoked Scottish Louch Trout and Lighthouse Bay Smoked Trout Trimmings, produced by St James Smokehouse. All use-by dates between Dec. 20, 2022, and Jan. 6, 2023, of Oak Smoked Scottish Louch Trout 100 grams and Lighthouse Bay Smoked Trout Trimmings 120 grams are affected.

In November, authorities said products had tested positive for Listeria but were within the maximum permitted level set in legislation. A limit of 100 Colony Forming Units per gram (CFU/g) applies to foods that can support the growth of Listeria, during the product’s shelf-life.

Given the product was compliant with microbiological regulatory limits yet still posed a risk to vulnerable consumers, authorities said it was critical that interventions ensured enforcement of food safety controls as well as public health messaging so people can understand the risks.

A spokesperson for Food Standards Scotland said: “During testing, Listeria monocytogenes that matches the outbreak strain was found in products produced by St. James Smokehouse and sold by Lidl. The levels found have not been above-permitted limits, but the strain of Listeria has characteristics that make it more dangerous to vulnerable consumers.”

Advice to consumers
Junior Johnson, director of operations at the FSA, said an investigation into the outbreak identified a strain of Listeria monocytogenes which has caused serious illness.

“As we approach the peak of the festive season, we know consumers are more likely to eat smoked fish, such as smoked salmon and trout. While investigations into the outbreak continue, FSS and FSA are reminding vulnerable consumers of the advice more generally around consuming smoked fish — it must be heated until it is steaming hot before they eat it,” he said.

Johnson also praised Lidl for “doing the right thing” in taking the recall action.

Listeria is ubiquitous in the environment, and there is no stage in the production of cold smoked salmon that can eradicate the organism, so it is extremely difficult to reduce the risk to zero. Controls are focused on good hygiene practices to minimize the risk of contamination and ensuring shelf life does not allow the pathogen to reach levels capable of causing illness, said Food Standards Scotland.

Advice to people over the age of 65, pregnant women or people with weakened immune systems is they should thoroughly cook ready-to-eat smoked fish before eating it. The warning covers chilled smoked fish products that would not normally be cooked at home before being eaten.

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Mortadella sold by Veroni is being looked at as a potential source but an official link has not been confirmed by authorities.

In early November, a number of recalls were published for Veroni mortadella due to potential Listeria contamination.

The Ministry of Health (Ministero della Salute) issued a warning covering a few batches of the Veroni Supergiant Mortadella packed in small portions due to the presence of Listeria monocytogenes.

Veroni said it immediately and voluntarily alerted the market, recalling all batches of Supergiant Mortadella with and without pistachios in portions that had expiry dates before Dec. 27, 2022.

In a statement to Food Safety News, Veroni said it had not yet been informed of any ongoing investigation and the issue doesn’t affect products sent to the United States.

“The cured meats imported in the U.S. by Veroni are manufactured in a dedicated facility based in the Emilia-Romagna region that serves only North America. Before being shipped, these products are subjected to high-pressure processing (HPP) treatment, leading to the inactivation of pathogenic microorganisms and enzymes in the food. In particular, the ready-to-be-sliced mortadella shipped in the U.S. is cooked at high temperatures and encased into artificial casings to prevent environmental contamination.

“In addition, all the products imported to the U.S. by Veroni are subjected to USDA inspection. Once delivered to Veroni’s NJ-based facility, the cured meats are sliced and packed following strict food safety and hygiene procedures. Daily inspections are conducted to minimize potential food safety risks and mitigate any problems. All Veroni’s facilities in Italy and the U.S. were inspected, further sanitized, and checked by government veterinarians: they are all working and safe.”

Unrelated to other Listeria outbreak

The latest outbreak is caused by a different type of Listeria than the one that has sickened at least 90 people and killed three since 2021.

Investigations previously revealed a connection between patients and the presence of Listeria in sausages made with poultry meat produced by Agricola Tre Valli, after sampling at the plant in Verona. Listeria was also detected during environmental sampling at the factory. Authorities have identified the same type of Listeria in some patients and recalled products.

AIA Wudy and Pavo brands have been recalled but they were distributed to 30 countries mostly across Europe including Austria, Belgium, Denmark, France, Germany, Netherlands, Spain, Sweden, and the United Kingdom.

There are sporadic cases in other countries but the major burden is in Italy, where recalls and investigations have been undertaken, said the European Centre for Disease Prevention and Control (ECDC).

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The models need to be tested and reviewed before being made public, said experts at a meeting organized by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations.

Findings come from a Joint FAO/WHO Expert Meeting on Microbial Risk Assessment (JEMRA) of Listeria monocytogenes in foods in October. The focus was on leafy greens, frozen vegetables, cantaloupe, and ready-to-eat (RTE) seafood. A summary has been released but a full report will be published later as part of the FAO and WHO Microbiological Risk Assessment (MRA) series.

Outbreaks of listeriosis continue to occur globally, with some linked to previously unreported food vehicles, such as leafy greens, melons, frozen vegetables, and ready-to-eat fish.

Data needed for models

Following recommendations from JEMRA in 2021, Codex — an organization that determines international food safety standards — is looking to update guidance on the control of Listeria monocytogenes in food.

Laurent Guiller, from ANSES in France, chaired the meeting and said it allowed scientists to develop the structure of four listeriosis risk assessment models.

“For three of them, the starting point is the contamination by Listeria monocytogenes at the primary production stage. We also worked collectively to establish a method to integrate genomic data. The expert group’s approach is flexible. It opens the way for different users around the world, with different levels of information, to evaluate the effectiveness of control measures along the production chain up to consumption,” Guiller said.

Scientists said the primary production (pre-harvest) module should enable assessment of the introduction of the pathogen in raw materials, taking into account the effects of season, agrifood practices, and climate change. The possibility of cross-contamination and recontamination from primary production to consumption should also be considered.

The dose-response model will be adapted from existing models that consider variability in pathogen virulence and consumer susceptibility. The inclusion of whole genome sequencing (WGS) and other -omics data on Listeria monocytogenes may also inform risk assessments.

Experts said an analysis should be performed to identify which model inputs and assumptions have the greatest impact on the outputs. More data on Listeria in the food chain from different sampling and testing schemes is also needed.

Key areas for lettuce and other leafy greens

For leafy greens, production steps including irrigation, fertilization, and other on-farm management practices impact the occurrence of Listeria and could be modeled. Relevant stages for the risk assessment include growth in a field, controlled environment or hydroponics, harvesting, cooling, washing, sanitizing, cutting, packaging, transportation steps, display at retail, and consumer practices.

Any model should measure the effectiveness of the prevention of contamination by soil/irrigation water, the efficacy of washing with or without sanitizers, the prevention of cross-contamination along the production chain, good hygiene practices during processing, the efficacy of sampling schemes, and the impact of different consumers’ practices related to handling and storage.

These points were also raised for cantaloupe. Experts said the risk assessment should consider cross-contamination at pre-harvest, at processing due to pooling of fruits from other producers, food contact surfaces, equipment or dicing, at retail, and at the consumer level from contamination from rind to flesh during slicing. They added the effect of time and temperature in the supply chain was also important to include.

Frozen vegetables and seafood

Relevant stages in the frozen vegetable risk assessment include cleaning, washing, blanching, freezing, packaging, retail display, and consumer practices such as defrosting, cooking, and non-intended use. The assessment should measure the effectiveness of blanching or other inactivation steps pre- or post-packing, prevention of contamination post-blanching, and efficacy of sampling schemes.

Hot- and cold-smoked and gravad fish represented the RTE seafood model. The risk assessment should be flexible to accommodate other RTE fish products in the future like sashimi or ceviche.

Cross-contamination should be in the model because fish is produced in several steps, either in one plant or multiple facilities in different countries. The effect of lactic acid bacteria cultures on the control of Listeria should be evaluated in the risk assessment and it should consider raw materials with different levels of contamination.

Earlier this year, FAO and WHO published a report as part of the MRA series on Listeria monocytogenes in ready-to-eat foods. A meeting in 2020 identified several gaps in the FAO/WHO risk assessment model and agreed updating it would be valuable to inform risk analysis strategies.

Another MRA series report covered control measures for Shiga toxin-producing E. coli (STEC) associated with meat and dairy products. There is no single solution to control STEC in all situations. Instead, multiple interventions at several points in the supply chain will be most effective.

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Food Standards Scotland (FSS) and the Food Standards Agency (FSA) suspect the source of contamination to be a salmon-smoking processing factory in Scotland.

Food Standards Scotland wouldn’t name the company or answer questions about the incident from Food Safety News.

Instead, a spokesperson said: “This is an ongoing outbreak of Listeria monocytogenes and, as yet, no definitive source of contamination has been found. Investigations to determine the root cause continue. Investigations of any outbreaks of foodborne illness will comprise both patient questionnaires and sampling of products.

“Local authorities are responsible for working on mitigations with any implicated businesses, and FSS, alongside partners the UK Health Security Agency, Public Health Scotland, and the Food Standards Agency, have been involved in raising awareness of the outbreak with consumers, most recently with targeted messaging to vulnerable groups.”

There have been 14 confirmed Listeria monocytogenes cases in just under two years. At least 10 sick people are above 65 years old, and one was a pregnant woman.

Three people older than 65 have died and for two Listeria monocytogenes was a contributory cause of death. All cases had underlying health conditions.

Of the linked cases of listeriosis since October 2020, eight have been identified since January 2022. The majority of them reported eating ready-to-eat smoked fish.

Challenging incident

Products sold by the unnamed implicated company have all been within the maximum permitted level set in legislation.

The limit of 100 Colony Forming Units per gram (CFU/g) applies to foods placed on the market, during the product’s shelf-life.

Businesses that produce foods that can support the growth of Listeria are expected to show, to the satisfaction of authorities, that the product will not exceed 100 CFU/g throughout the shelf-life. Or, they must prove absence in 25 grams before the food has left their control.

“Food law is written on the basis of reducing risk as far as is reasonably practicable. It does not equate to an absence of risk, but an acceptance that residual risk will remain. Listeria is ubiquitous in the environment, and there is no stage in the production of cold smoked salmon that can eradicate the organism. Therefore, it is virtually impossible to reduce the risk to zero,” said Food Standards Scotland.

Controls are focused on good hygiene practices to minimize the risks of contamination and ensuring shelf life does not allow the pathogen to reach levels capable of causing illness. However, epidemiological data has shown that doses as low as 8 CFU/g can cause illness in vulnerable consumers susceptible to foodborne disease.

Given the product is compliant with microbiological regulatory limits yet still poses a significant risk to vulnerable consumers, authorities said it is critical that interventions ensure effective enforcement of food safety controls as well as public health messaging which enables people to understand the risks.

Advice to people over the age of 65, those who are pregnant or have weakened immune systems is that they should thoroughly cook ready-to-eat smoked fish before eating it. The warning covers chilled smoked fish products that would not normally be cooked at home before being eaten.

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From mid-August to October, the Statens Serum Institut (SSI) recorded seven patients who became ill with the same type of Listeria monocytogenes.

The Statens Serum Institut, Danish Veterinary and Food Administration (Fødevarestyrelsen), and DTU Food Institute investigation pointed to a brand of fish cakes that have now been recalled.

Patients are three men and four women. Those sick include one child and six people over the age of 70, one of whom has subsequently died.

Ill people live across the country and interviews with six patients showed they had all eaten fish cakes.

Product recall
Earlier this week, Jeka Fish recalled all fish cakes produced between Aug. 1 and Nov. 8. Items have shelf life dates ranging from Sept. 6 to Dec. 14 this year. A frozen product with the same production dates but an expiry of Jan. 31, 2024, to May 7, 2024, is also affected. Products were sold at SuperBrugsen, Kvickly, Dagli’Brugsen, Irma, Coop365, Fakta, Netto, Bilka, Lidl and Aldi stores and online.

The action was taken because the Danish Veterinary and Food Administration found Listeria in the production environment and in products from the company. The same type of Listeria has so far been found in patients and the production environment.

Jeka stopped production for a thorough cleaning and disinfection of the facility and equipment.  

The fish cakes have also been sent to Finland, Germany, Italy, Latvia, Romania, and Slovakia.

SSI is responsible for whole genome sequencing of Listeria isolates from patients and interviewing patients or relatives.

“When comparing bacteria from patients and samples from Jeka Fish, we have found that they are exactly the same. Combined with the fact that patients stated they have eaten fish cakes, this shows that the infection came from here,” said Luise Müller, an epidemiologist at the Statens Serum Institut.

Whole genome sequencing of bacteria isolated from patients showed samples were closely related and all belonged to sequence type 7.

Since October, Denmark has recorded significantly more infections with other types of Listeria than in previous years. Officials are continuing work to try and find the causes of these other cases.

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It was the largest listeriosis outbreak in Spain and one of the biggest in Europe. Based on hospitalization records, Spain has seen a rising trend in such infections since 1997, reported the study published in the journal Eurosurveillance.

Between July and October 2019 in Andalusia, an outbreak with 207 cases of listeriosis was identified. Confirmed cases had a median age of 44 with a range of 0 to 94 years old and 114 were women.

Four provinces were affected with 163 confirmed patients in Seville, 29 in Huelva, 11 in Cadiz and four in Malaga. In Andalusia, stuffed pork is popular, as it is a low-cost, traditional ready-to-eat (RTE) food. It consists of a cold cut of roasted pork with garlic, spices, and salt.

Patient details
Most sick people had mild gastroenteritis, 141 required hospitalization and three died; five of 34 pregnant women had a miscarriage. The three patients who died were above the age of 70. The median incubation period was one day with a peak of 43 patients notified on a single day in mid-August.

Stuffed pork, an RTE product consumed unheated and contaminated with Listeria monocytogenes sequence type 388 was identified as the source of infection. The “La Mecha” brand chilled pork was produced by Magrudis. Most cases reported having purchased the stuffed pork at a variety of establishments but primarily supermarkets and bars.

Facua, a consumer group, is representing about 80 sick people, as part of a civil action. A criminal trial is ongoing with certain staff at the company facing up to 10 years in prison and a local veterinarian who carried out inspections at Magrudis also facing charges.

Active case finding identified 16 additional WGS-confirmed patients before the outbreak started by several months with illness onset dates from November 2018 to June 2019. Epidemiological interviews revealed only one sick person had contaminated meat. So, they have deemed historically associated cases and are not included in the outbreak investigation.

An additional 11 outbreak cases came from six different regions in Spain. French authorities notified a confirmed case of an individual who had consumed pork meat in Seville in mid-August. A link to several cases of listeriosis in Germany could not be established by public health authorities.

Investigations by authorities
The outbreak strain was identified in 189 human samples, 82 food, and five environmental samples.

The first inspection at the Magrudis plant in mid-August 2019 found no positive samples. However, there were four contaminated food and five environmental samples were identified within the first 10 days. During the next two months, 55 additional food samples from the factory were found to be contaminated. Most were taken between mid and the end of August.

Listeria monocytogenes was quantified in 42 food samples with values well above the limit set by European Union regulations of 100 colony-forming units per gram (CFU/g).

A public health alert was announced in mid-August 2019. The next day, cleaning and disinfection of the Magrudis plant were done and stuffed pork from the site was recalled. A few days later, production was stopped and the recall expanded to any meat produced in the facility before it was extended again to include every food product. The recall was estimated to include more than 8 tons of meat products.

By the end of the outbreak, Listeria monocytogenes were detected in 87 samples. Most positives came from products involving stuffed pork and other pork items.

The remaining five samples were environmental, mostly from machinery surfaces. These included an oven trolley, meat injectors, which are metal syringes used to add condiments to meat, and an air conditioner vent. Eight food samples were shown to harbor the outbreak strain by WGS.

Poor hygiene conditions at the site could explain the contamination of meat products, which might have happened after thermal treatment and before delivery to grocers or sellers. There is also a need to improve food distribution records. Identification of all the establishments to which the stuffed pork had been sent was not as fast as desired, said researchers.

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Between Aug. 18 and Oct. 13, the Statens Serum Institut (SSI) recorded five people infected with the same type of Listeria monocytogenes.

Two men and three women are sick. Patients are between the ages of 6 and 83 years old with a median age of 75. Two ill people live in Syddanmark and one each in Sjælland, Midtjylland, and Hovedstaden.

All five patients have been hospitalized but none of them have died.

Searching for the source
The Statens Serum Institut (SSI), Danish Veterinary and Food Administration (Fødevarestyrelsen), and DTU Food Institute are investigating the outbreak.

SSI is interviewing patients about their food consumption history before illness to identify a possible source of infection.

Whole genome sequencing of bacteria isolated from patients showed samples were closely related and all belonged to sequence type 7.

This sequence type is different than the one behind a Listeria outbreak that infected nine people from mid-May to early June 2022. All patients were hospitalized and four people died within 30 days of a sample being taken.

In another unrelated outbreak, 12 people were infected with the same type of Listeria since October 2020. Two cases were reported in 2020, nine in 2021, and one in May 2022. Three people died and all were hospitalized.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has developed symptoms of Listeria infection should seek medical treatment and tell their doctor about possible Listeria exposure.

Also, people should monitor themselves for symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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The Ministry of Health (Ministero della Salute) said the most recent patient was reported in mid-September.

Deaths occurred in December 2021 and March and June 2022 in Lombardy, Piedmont, and Emilia Romagna. The patients were immunocompromised or particularly vulnerable to infection. One woman lost her baby in the outbreak.

Patients live in Piedmont, Lombardy, Veneto, Emilia Romagna, Liguria, Umbria, Tuscany, Calabria, Lazio, Puglia, Valle D’Aosta and Abruzzo.

The Ministry of Health created an outbreak working group, which includes the Italian National Institute of Health (Istituto Superiore di Sanità), National Reference Laboratories, and regional agencies that met in August and were made official in September.

There are also sporadic cases in other countries but the major burden is in Italy, where recalls and investigations have been undertaken, said the European Centre for Disease Prevention and Control (ECDC).

Ongoing work after recall
Investigations in Italy previously revealed a connection between patients and the presence of Listeria in sausages made with poultry meat produced by Agricola Tre Valli, after sampling at the plant in Verona. Listeria was also detected during environmental sampling at the factory.

Authorities have identified the same type of Listeria in some patients and the recalled products but have not been able to link all patients to one product.

Positive batches with codes 1785417 and 01810919 plus all items produced before Sept. 12 were recalled. It included the AIA Wudy and Pavo brands with expiration dates through Dec. 5, 2022.

Chicken and turkey sausages with cheese were distributed to 30 countries mostly across Europe including Austria, Belgium, Denmark, France, Germany, Netherlands, Spain, Sweden, and the United Kingdom.

Data from the National Institute of Health shows cases of Listeriosis decreased by more than 27 percent in 2020 compared to 2019, but have been increasing again in the past two years.

An earlier statement from Agricola Tre Valli said the voluntary withdrawal involved some hot dogs with the CE mark IT 04 M but production was continuing.

“The cooperative company has started this procedure in a precautionary way in agreement with the Italian authorities because the incorrect storage of the products and the non-compliance with the instructions on the labeling could make the food not suitable for consumption from a microbiological point of view,” said the company.

“The company also specifies that it has always operated in full compliance with the laws in force. These procedures have been followed also for the batches that are involved in the current withdrawal.”

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In total, 124 cases of listeriosis were reported in England and Wales in 2020, which is the lowest amount in several years. In 2019, 144 cases were recorded.

There were two outbreaks in England. One was a national epidemic with four cases associated with smoked salmon. Two people died. The other caused two illnesses from 2018 to 2020 and was linked to prepacked sandwiches served in hospitals.

Surveillance of listeriosis in England and Wales is coordinated by the Gastrointestinal Infections and Food Safety (One Health) Division at the UK Health Security Agency (UKHSA). New cases are reported by local clinical laboratories, and health protection teams and by the referral of Listeria monocytogenes isolates to the Gastrointestinal Bacteria Reference Unit (GBRU) for whole genome sequencing (WGS).

Incidence rates were highest in people aged 80 years and older.

Often a serious infection
Overall, women were more affected than men. However, reported cases among men aged 60 to 69 were four times higher than in women in this age bracket. Of 21 cases in people aged 10 to 39, 19 were female and 16 were associated with pregnancy.

Pregnancy-associated infections accounted for a sixth, or 25 cases, which was a higher percentage than in previous years. More than a third of such cases resulted in stillbirth or miscarriage.

Overall, 29 people died and 17 had listeriosis recorded as a cause of death on the death certificate.

Incidence varied geographically, with the lowest in the North West and the highest in the East Midlands. In Wales, eight cases were reported.

October was the peak month for listeriosis reporting in 2020, with no outbreak influence. In 2019, case numbers peaked in May, with one outbreak influencing this finding.

Between January and October 2020, an outbreak was detected in England involving four people, including a pregnancy-related case. One sick person reported consuming salmon trimmings and smoked salmon slices purchased from a UK supermarket chain.

Whole genome sequencing analysis of food isolates from smoked salmon in an EU country identified the outbreak strain. Samples were traced back to a salmon supplier in the UK that distributed products to the retailer reported by one patient.

Listeriosis is a rarely reported disease in England and Wales but the outcome of infection in pregnancy-related cases remains severe, said, officials.

“Two national outbreaks were traced back to high-risk foods for listeriosis. As a predominantly foodborne infection, awareness of high-risk foods for vulnerable groups is vital. It remains imperative that sporadic cases of illness and clusters of the disease continue to be monitored and investigated to inform the continued risk assessment of the food chain.”

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The study, titled “Quantitative risk assessment model to investigate the public health impact of varying Listeria monocytogenes allowable levels in different food commodities: A retrospective analysis” was led by Fernando Sampedro of the Environmental Health Sciences Division, School of Public Health at the University of Minnesota.

The study found the total number of estimated listeriosis cases in the U.S. was between 1,044 and 2,089, and the probability of infection in the U.S. susceptible population — individuals such as elderly, pregnant women, and neonates and people with underlying disease conditions or comorbidities — to be 10–10,000× higher than the general population. This highly susceptible population makes up 46.9 percent to 80.1 percent of total listeriosis cases.

The main objectives of this study were to first, perform a retrospective analysis of the changes in prevalence and concentration levels of Listeria monocytogenes in various commodities (RTE salads, deli meats, soft and semi-soft cheese, RTE seafood, and frozen vegetables) over the last 30 years.  And second, to estimate the net public health effect of removing lots with certain contamination levels from the market.

The study found that after deli meat at more than 90 percent and RTE salads at just less than 5 percent, soft and semi-soft cheese and RTE seafood accounted for 0.5 to 1.0 percent of listeriosis cases. Lastly, frozen vegetables accounted for 0.2 to 0.3 percent of cases.

The study suggests that introducing lot-by-lot testing and defining allowable quantitative regulatory limits for low-risk RTE commodities may reduce the public health impact of L. monocytogenes and improve the availability of enumeration data. The researchers hope the study provides guidance to national authorities as they formulate effective risk management strategies that account for differences in risk levels to optimize the use of threshold values in implementing preventive controls for L. monocytogenes.

The complete study can be found here.

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Patient samples were taken between February and August this year and all ill people were hospitalized.

Those affected are aged between 50 and 90 years old. The patients are two women and two men who live in Nordland, Trøndelag, Oslo and Viken.

The Norwegian Institute of Public Health (FHI) said bacteria with the same genetic profile have been found in samples from all four patients, which indicates they were infected by a common source. There is also one suspected case.

Troll Salmon has recalled smoked trout and smoked salmon due to possible Listeria monocytogenes after the pathogen was found in the production environment.

FHI, local health services and microbiological laboratories, the Norwegian Food Safety Authority (Mattilsynet) and Veterinary Institute investigated whether patients had a common source of infection.

Three of four patients interviewed by the Norwegian Food Safety Authority said they ate smoked salmon or smoked trout before they became ill and two of them named smoked salmon from the same producer.

Detected Listeria does not match outbreak strain
Listeria had been found at low levels in a product from Troll Salmon earlier in the year. This sample was a routine test taken as part of the Norwegian Food Safety Authority’s monitoring program for ready-to-eat products in 2022. Officials said the amount of Listeria in the sample was so low that it posed no health risk.

After an inspection at Troll Salmon, several environmental samples were analyzed at the Veterinary Institute. Listeria monocytogenes was found in some of them but isolates did not match the outbreak strain.

However, the Norwegian Food Safety Authority told the company to remove several products from the market.

The recall affects certain batch numbers of sliced smoked trout with pack sizes 250-grams, 200-grams and 100-grams and sliced smoked salmon 250-grams, 120-grams and 100-grams. Products have expiry dates from Oct. 17 to Nov. 10, 2022.

Almost 20,000 packs were sent to retail chains Rema 1000, Coop, and NorgesGruppen across the country or sold online.

Troll Salmon advised consumers who had bought the products to throw them away or return them to the place of purchase. The company is taking steps to find the source of the outbreak strain and extra cleaning of the site and equipment has been carried out.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has eaten any recalled product and developed symptoms of Listeria infection should seek medical treatment and tell their doctors about the possible Listeria exposure.

Also, anyone who has eaten any of the recalled products should monitor themselves for symptoms during the coming weeks because it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop. 

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses. 

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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