Reports of most major pathogens increased in Switzerland in 2024 and the country continued to battle a serious Listeria outbreak.
The Federal Food Safety and Veterinary Office (FSVO) reported that Campylobacter, Salmonella and E. coli infections went up but Listeria cases declined.
Campylobacteriosis remained the top recorded infection in humans. A total of 8,280 laboratory-confirmed cases were reported compared to 6,762 in 2023.
In 2024, 2,081 cases were reported during July and August. Men were slightly more affected than women, a finding that applies to all age groups
Key pathogen data
Salmonellosis was the second most common infection with 2,344 lab-confirmed patients, which is up from 1,623 in 2023.
The most frequently reported serovars remained the same with Salmonella Enteritidis in first, followed by Salmonella Typhimurium and the monophasic variant of Salmonella Typhimurium.
With 1,361 cases in 2024, there was a further increase in Shiga toxin-producing E. coli (STEC) compared to 1,225 in 2023. The resulting reporting rate is the highest since mandatory reporting was introduced in 1999. Whether the rise can be explained by increased testing thanks to multiplex PCR methods, improving the frequency of detection, is currently unclear, said FSVO, which is also known as BLV and OSAV.
Except for children younger than 4 years old, women were affected slightly more frequently than men, regardless of age. A possible country of exposure was mentioned in 628 cases, with Switzerland named in 398 cases.
With 19 cases of Hemolytic Uremic Syndrome (HUS) in 2024, the figures remained stable compared to previous years. Seven children younger than 5 years of age and four people more than 65 years old were affected.
In 2024, 51 cases of Listeria monocytogenes were reported, which was down from 74 in 2023. Whole genome sequencing allowed 22 cases to be assigned to a single cluster and the source of infection to be identified in three clusters.
As in previous years, the highest reporting rate was recorded in the older than 65 age group. Men were affected slightly more often than women.
Major Listeria outbreak
A total of 43 outbreaks were reported by Swiss inspection authorities in 2024. At least 347 people fell ill, 16 were hospitalized and there were two deaths. One outbreak affected 14 cantons and has been ongoing since 2022.
The agent was known in 15 outbreaks with four each because of E. coli and Campylobacter. Norovirus and Staphylococcus both caused three and two were due to Bacillus cereus. Listeria, Salmonella, and Clostridium perfringens all caused one outbreak.
Egg sandwiches, marinated raw tuna, kebabs, raw milk, paella, and rice were suspected sources of infection.
A nationwide listeriosis outbreak has been ongoing for three years, affecting 38 people, including eight deaths. In 2024, eight cases and two deaths were recorded.
After an extensive investigation, the same strain of bacteria was found in baker’s yeast products from a factory and its production lines. However, even after the suspected source was identified and strict measures were implemented at the factory, new cases emerged. Officials said the outbreak highlights the difficulty of tracing the exact origin of infections and the risks of cross-contamination associated with non-ready-to-eat products such as yeast. The outbreak remains under investigation, with inquiries involving health and judicial authorities.
In June 2024, two classes of students aged 5 to 6 participated in a farm trip. During the day, children consumed raw milk. Three days later, 10 of them developed symptoms, and three required medical attention. Stool tests revealed the presence of Campylobacter jejuni.
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