Tomatoes are the probable source of a Salmonella outbreak in Sweden that affected 70 people, according to public health officials.
Folkhälsomyndigheten (Public Health Agency of Sweden) identified 71 infections from 11 counties that belonged to the outbreak. This is up from 36 illnesses in 10 counties that were linked by whole genome sequencing at the end of September. Västra Götaland, Jönköping, Halland and Dalarna reported the most patients.
Illnesses were recorded in all age groups with 46 women and 25 men ill. Of the cases so far linked to the outbreak, the last known date of illness onset was Sept. 19.
Case control study; no positive samples
Local disease infection units, Livsmedelsverket (Swedish Food Agency) and Folkhälsomyndigheten investigated the monophasic Salmonella Typhimurium outbreak. Analysis of the Salmonella bacterial genome showed disease cases were related and it is likely they were infected by the same source.
Folkhälsomyndigheten did a case-control study to compare what those sick ate the week before they became ill with what healthy control people had eaten. Results showed that those who were ill had eaten tomatoes to a greater extent than the healthy control people.
An investigation found the tomatoes were in supermarkets at the end of August, but since they are fresh, there is no longer any stock left in grocery stores. Product testing was done but no tomatoes were positive for Salmonella.
Authorities said the risk of being infected with Salmonella from fresh tomatoes was very small.
The outbreak strain has multilocus variable-number tandem-repeat analysis (MLVA) pattern 3-12-11-N-211.
Most people infected with Salmonella develop signs 12 to 72 hours after being exposed to the bacteria. Symptoms can include diarrhea, fever, abdominal cramps and vomiting that lasts for several days.
Otherwise healthy adults are usually sick for four to seven days. Older adults, children, pregnant women and people with weakened immune systems, such as cancer patients, are more likely to develop a severe illness and serious, sometimes life-threatening conditions.
Meanwhile, Livsmedelsverket has warned people to correctly soak and cook dried legumes such as beans, peas and lentils after they were linked to a large food poisoning outbreak at a school.
Dried legumes naturally contain lectins which can cause nausea, vomiting and diarrhea around one to seven hours after consumption.
Illness occurred in the canteen at lunchtime in early September at Baldergymnasiet school in Skellefteå, a city in Västerbotten County. Swedish media reported almost 280 people were affected and samples were sent to a laboratory in the United Kingdom.
Sandra Wallström, a food inspector at Skellefteå municipality, said it was thought to be the first time that elevated levels of lectin have been shown to have caused food poisoning in Sweden.
Follow-up checks will be made at the school to ensure the handling of beans and similar foods is safe in the future.
Swedish officials urged people to follow instructions on the packaging and in recipes. They should be soaked for at least 12 hours, rinsed and cooked for at least half an hour. Canned beans are already cooked and can be eaten directly without soaking and boiling.
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