Norovirus caused the most foodborne outbreaks, but Salmonella was behind the largest, according to an analysis covering several years in Finland.

In 2020 to 2022, there were 135 foodborne outbreaks included in a register maintained by the Finnish Food Authority (Ruokavirasto). Overall, 2,543 people fell ill, 86 were hospitalized, and 15 died.

A total of 55 outbreaks were recorded in 2022, 46 in 2021, and 34 in 2020, according to the report published by Ruokavirasto and the Finnish Institute for Health and Welfare (THL).

Norovirus was the most common cause of foodborne outbreaks in the period with 34. Contaminated oysters were linked to five norovirus outbreaks. Salmonella was behind 13 outbreaks with 226 cases, Campylobacter caused 12 with 101 cases, Listeria caused seven with 69 cases, five were due to Yersinia enterocolitica with 40 cases and three because of E. coli with 90 cases. The causative agent was unknown in 33 outbreaks.

Outbreak details by pathogen
Salmonella Typhimurium caused the most significant event in June 2021, when 728 people became ill because of a salad mix in lunches served in daycare centers. More than 100 staff fell sick and 620 patients were children. More than 50 sites received food from the same central kitchen.

Salmonella mbandaka caused the biggest outbreak in 2022 and was part of an EU-wide incident linked to chicken. A total of 97 people were sick in Finland. A serious E. coli O103 outbreak affected 62 people in 2021. Two people developed hemolytic uremic syndrome (HUS), and two died. Salad products were suspected, but food testing didn’t find the outbreak strain.

Two Listeria clusters, one with 23 cases between 2016 and 2020 and the other with 14 cases in the same time period, were linked to meat products.

Most foodborne epidemics were small, with fewer than 10 cases. Two had more than 100 patients; the rest were medium-sized, with 11 and 100 cases.

Bacillus cereus caused three epidemics in 2020 and 2022, in which 28 people fell ill. One of these was traced to a contaminated oat drink. Clostridium perfringens also caused three outbreaks and 62 people were sickened. Two ETEC outbreaks affected 39 people. One outbreak each was due to histamine, with nine cases, and Cryptosporidium, with 35 cases.

Foods and reasons for outbreaks
The most reported food vehicles were vegetables and products, with 16 outbreaks. The second most common was fish and fish products, including shellfish and mussels, with 12 outbreaks. However, the vehicle remained unidentified in most outbreaks, or several foods were suspected.

imported frozen raspberries caused one Hepatitis A virus epidemic with five cases. A Hepatitis E outbreak sickened four people in 2022. E.coli and Cryptosporidium caused illness in an outbreak traced to raw milk cheese. Another small E. coli outbreak was linked to raw milk.

The participation of an infected kitchen worker in food preparation and inadequate hand hygiene resulted in 23 outbreaks. In nearly all these cases, the causative agent was norovirus. The use of contaminated ingredients was linked to 18 outbreaks. In 16 outbreaks, there were inadequacies and errors in temperatures and storage of food.

The main locations wher outbreaks occurred were restaurants, cafés, or hotels, with 64 outbreaks, followed by homes, with 16 outbreaks. Sixteen national outbreaks or outbreaks with multiple locations were also reported.

Meanwhile, data from Helsinki shows more reports of suspected food poisoning in 2023 than the year before. However, investigated outbreaks dropped from 18 to 13. A total of 245 people fell sick.

Suspected food poisoning alerts rose to 795 from 654 in 2022. This trend may be related to increased restaurant dining or better operator awareness of the need to report incidents. In most suspected food poisonings, the cause remained unclear, or the illness was unrelated to the outlet.

Of 13 food poisoning outbreaks, Norovirus caused four. Three were linked to an infected kitchen worker, and the other was due to oysters. Contaminated oysters caused 150 people to fall ill after eating at different restaurants. Norovirus was found in Dutch, French, and Irish oysters, and several batches of products were removed from the market.