The number of people sick has gone up in Denmark, but the number of outbreaks remained stable in 2022, according to recently released data.

In 2022, there were 5,142 cases of Campylobacter and 899 cases of Salmonella, compared to 3,740 and 692 in 2021. Of Campylobacter and Salmonella cases in the past year, 28 percent and 40 percent were travel-related.

Overall numbers increased for the second year in a row and are back at the same level as before the COVID-19 pandemic, according to the annual report on zoonoses in Denmark.

A total of 63 foodborne outbreaks, with 1,284 patients, were reported in 2022, compared to 63 outbreaks and 1,257 patients in 2021. The largest incident in 2022 affected 125 people.

Norovirus was the leading cause of foodborne outbreaks, causing 14 affecting 614 people. The most common way of acquiring infection was through exposure to symptomatic or asymptomatic healthy carriers among the kitchen staff. Four outbreaks were related to oysters.

Salmonella, Listeria and E. coli
Salmonella caused 11 outbreaks in 2022, with three-part of international incidents. The largest was because of Salmonella Enteritidis, with 24 cases reported between March and September. The source could not be identified, but chicken products from Poland were suspected.

Salmonella Enteritidis and Salmonella Typhimurium, including the monophasic variant, were the top Salmonella types involved in illnesses. Six cases were recorded in an international Salmonella Jukestown outbreak and three in a Salmonella Ball outbreak.

A total of 86 cases of listeriosis were reported in 2022 compared to 62 in 2021. This included six outbreaks, with the source identified for two of the larger epidemics. Likely sources were ready-to-eat (RTE) spiced and sliced meat rolls, known as rullepølse, which sickened nine people, and fish patties, which affected 10.

For six older outbreaks, two or more cases were identified in 2022. Three other outbreaks have seen eight to 14 cases in the past three to five years, but the sources remain unknown.

There were 1,330 cases of Shiga toxin-producing E. coli (STEC), up from 927 in 2021. When information on the type was known, it was most often O157, followed by O26, O103, and O146. A STEC O26 and Campylobacter incident affected five people who drank raw cow’s milk.

Campylobacter focus
The Central Outbreak Management Group, which includes the DTU National Food Institute, Statens Serum Institut, and the Danish Veterinary and Food Administration, investigated 11 Campylobacter outbreaks, including five caused by contaminated Danish chicken meat. This past year the group focused on early detection of outbreaks.

“The threshold for investigating Campylobacter outbreaks was lowered in 2022 to five recorded cases. This means that we’ve investigated more Campylobacter outbreaks than in previous years,” said Annette Perge, from the Danish Veterinary and Food Administration (Fødevarestyrelsen).

In 2022, a new action plan for Campylobacter was implemented. One aspect is that each slaughterhouse will be accountable for its ability to ensure that the presence and concentration of bacteria in chicken products are kept below certain thresholds and lowered to under the slaughterhouse’s previous level. 

“Since 2019, the Danish Veterinary and Food Administration and Statens Serum Institut have monitored Campylobacter in sources and humans through whole genome sequencing, which is a method for analyzing the DNA of microorganisms. Because of this, we’ve detected many more outbreaks and have found that the source is very often chicken meat,” said Luise Müller, epidemiologist at Statens Serum Institut.

Yersinia enterocolitica cases increased from 454 to 747 in 2022. Two outbreaks sickened 15 people but the sources were not found.

Two lectins outbreaks were linked to a school and a kindergarten. In the school, 25 people fell sick after eating green lentils. In the kindergarten, 74 people were ill after eating a butter bean soup.

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