The number of foodborne infections climbed in Sweden in 2021 compared to the year before but most are still below pre-Coronavirus pandemic levels.
The report by the National Veterinary Institute (SVA), Folkhälsomyndigheten (the Public Health Agency of Sweden), Livsmedelsverket (the Swedish Food Agency) and Jordbruksverket (Swedish Board of Agriculture) showed a rise for Campylobacter, Salmonella, Listeria, E. coli and Yersinia infections.
Disease surveillance relies on patients seeking care and fewer people have done this during the pandemic. This is believed to be related to patients with symptoms choosing to not seek care and a true reduction in disease incidence because of changes in general hygiene such as increased handwashing, physical distancing and reduced travel because of COVID-19-related recommendations, according to the agencies.
Rise in Campylobacter cases and Salmonella outbreaks
A total of 4,059 cases of campylobacteriosis were reported in 2021 and 3,025 were domestic compared to 3,434 cases overall in 2020.
Incidence of domestic cases in 2021 increased by 23 percent from the year before. The rate of travel-related cases was at a record low, which makes the overall incidence the second lowest since the reporting system was introduced in 1997.
A large increase in people infected with Campylobacter was noticed in June with a peak in July-August. Also, in the surveillance program for chickens, a higher prevalence was noted from July through October. Most cases have been considered sporadic, but recent work has found many are part of outbreaks, which are often linked to poultry meat.
A total of 946 cases of salmonellosis were reported, compared to 826 in 2020 and 1,993 in 2019. Domestic cases increased from 422 in 2020 to 722 in 2021.
The most common types in domestic patients were Salmonella Enteritidis, monophasic Salmonella Typhimurium and Salmonella Typhimurium. Another 60 different serovars were identified in 2021.
Eleven outbreaks involving 10 or more cases were recorded, up from 2020 when only two such outbreaks occurred. These outbreaks accounted for 293 of the 722 domestic infections.
An outbreak of Salmonella Enteritidis linked to chocolate wafers was investigated where 19 of 34 cases were younger than 10 years old. The outbreak strain was identified in two of 22 analyzed samples of products from cases’ homes. Neither the company that made the wafers nor the control authority could find any Salmonella in the production line or the product.
Salmonella Coeln affected 53 people with sprouts as the suspected source and Salmonella Dublin has sickened 22 people between September 2019 and the end of 2021.
Sweden had 48 cases in the multi-country Salmonella Braenderup outbreak linked to melons from Honduras and 42 cases linked to six serotypes and eight different strains of Salmonella in the outbreak from tahini and halva produced in Syria.
More E. coli and Listeria cases recorded
In 2021, 653 cases of E. coli were reported and 530 were domestically acquired, compared to 491 overall cases in 2020.
STEC-associated Hemolytic Uremic Syndrome (HUS) was reported in 24 cases of which 23 were domestic infections in 2021. 16 HUS cases were children younger than 10.
In total, 80 different serotypes were identified. The most common types were O157:H7, O103:H2 and O26:H11.
Three outbreaks had cases spread across the country where the source was suspected to be food, but no source could be identified. Two were O157 and one was O103.
In total, 107 Listeria infections were reported compared to 88 in 2020. The median age was 78 and as in previous years, most cases were in the over 80’s age group. A total of 21 people died within one month of diagnosis.
In 2021, five cases of Listeria monocytogenes were linked to a cluster of 14 cases in Belgium. They were reported between 2014 and 2021 and the outbreak strain was detected in salmon from Norway. For Swedish cases, salted non-heat-treated salmon was the suspected source of infection.
The source of an outbreak with two cases was traced to a meat plant. One person had eaten a locally produced sausage. The outbreak strain was found in samples from equipment and processing areas. One cluster included 10 cases from 2021 and eight from 2019 but a source was not found.
Another case was linked to a local cheese. A sample of washed rind cheese from the refrigerator of the patient was positive for the outbreak strain. Cheese was made from pasteurized milk, but analysis of cheese and environmental samples from the dairy showed the premises was contaminated by the outbreak strain and it was isolated from a washed rind and a semi-hard cheese.
Yersinia, Cryptosporidium and Brucella
During 2021, 313 Yersinia infections were reported with the majority falling sick in Sweden versus 220 cases in 2020.
Sixteen people were ill after eating iceberg lettuce at a restaurant chain in early 2021.
A total of 524 cryptosporidiosis cases were recorded. Most people were infected in Sweden but 83 fell sick abroad. A total of 42 domestic cases were reported in January because of an outbreak that had vegetables as the suspected source.
In January, several illnesses were detected in a retirement home followed by cases in March among students and staff at two different schools in Jönköping county. Fourteen cases were positive for Cryptosporidium parvum. Kale and cabbage were suspected as the probable cause of infection. Kale was positive for Cryptosporidium parvum. Fecal matter from rodents and deer at the farm was sampled, but the source of contamination of vegetables was not established.
In 2021, 10 cases of brucellosis were reported. Patients had an age range of 25 to 78 years old and four were female. Two people acquired the infection in Iraq, two in Somalia, one in Afghanistan and one in Ethiopia and for three country of infection was unknown. For five cases, unpasteurized dairy products were the likely source of infection.
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