Date: Thu 25 Apr 2019
Source: Food Safety News [edited]
Swedish officials are investigating the source of infection as part of a national outbreak of _Yersinia enterocolitica_. The Public Health Agency (Folkhalsomyndigheten) reported there had been an increase in the number of cases of yersiniosis in the country since the start of March 2019. Since the outbreak strain of _Y. enterocolitica_ type O3 had been found in different parts of the country, it is likely a foodborne infection, added the agency.
A total of 26 cases have been confirmed, and another 30 infections are being investigated. Onset dates for confirmed cases range between 10 Feb 2019 to 3 Apr 2019. There have been no deaths reported, and information on hospitalization is not collected at the national level. Confirmed cases have a median age of 28 years (range 6-62 years old); 60% are women, and they live in different areas from the county of Halland in the south to Vasterbotten in the north.
Infection with _Yersinia_ is relatively rare in Sweden with between 200 and 300 cases reported annually. In 2004 more than 800 were recorded. A spokeswoman for Folkhalsomyndigheten told Food Safety News that cases have been confirmed as belonging to the outbreak, thanks to the use of whole genomic sequencing (WGS).
"When the number of cases increased, a request was sent out to the local clinical microbiological laboratories to send in _Y. enterocolitica_ isolates to the Public Health Agency of Sweden for typing using WGS. WGS could clearly either confirm or exclude cases," she said. "Patients have been interviewed, and most cases have also completed a trawling questionnaire. A case control study is ongoing, and we are also collecting receipts from grocery stores with the hope of finding a common denominator."
"It is too early to say (if the outbreak is over or not) since we still await WGS results from possible cases with more recent onset of disease. The incubation period is 3-7 days, generally under 10 days."
One link being investigated is from sampling during an official food control in Latvia in mid-March 2019, which found _Yersinia_ in snack carrots also sold in Sweden. The batch has already been sold out and is presumed to be no longer available to buy. The raw carrots came from Sweden and were packed in Denmark.
The Folkhalsomyndigheten spokeswoman said the only link to the snack carrots is the timing, and it has no information as yet that several cases ate this type of carrot. The agency is continuing to investigate the source of infection with affected municipalities and the National Food Agency (Livsmedelsverket).
Raw or undercooked meat consumption is often the cause of infection. Direct transmission from other animals such as pets or through contaminated food or drink is also possible. After an incubation period of 3-7 days, symptoms include fever, diarrhoea, and abdominal pain in the right lower part of the abdomen. [Byline: Joe Whitworth]
[The 2 species of _Yersinia_ associated with food-borne disease are _pseudotuberculosis_ and _enterocolitica_. The latter species can be associated with abdominal pain as a hallmark symptom. As a mesenteric lymphadenitis, yersiniosis can mimic appendicitis but may also cause infections of other sites, such as wounds, joints, and the urinary tract.
As noted in the FDA "Bad Bug Book" <https://wayback.archive-it.org/7993/20170406190140/https://www.fda.gov/Food/FoodborneIllnessContaminants/CausesOfIllnessBadBugBook/ucm070040.htm
>, "Strains of _Y. enterocolitica_ can be found in meats (pork, beef, lamb, etc.), oysters, fish, and raw milk. The exact cause of the food contamination is unknown. However, the prevalence of this organism in soil, water, and animals, such as beavers, pigs, and squirrels, offers ample opportunities for it to enter our food supply. Poor sanitation and improper sterilization techniques by food handlers, including improper storage, cannot be overlooked as contributing to contamination." Additionally, some strains of these organisms can be associated with blood transfusion-associated illnesses due to an ability to grow at refrigerator temperatures. - ProMED Mod.LL]