An investigation into a Salmonella outbreak in Sweden has resumed after more people fell ill.
From August to October, 81 people from 18 regions contracted Salmonella Typhimurium with sequence type (ST) 36. As far as information on the country of infection is available, all cases were infected in Sweden.
Folkhälsomyndigheten (the Swedish Public Health Agency) reported that patients have been infected with one of about ten different but genetically related bacterial variants that have caused illness.
Further cases after the initial work
IIn September, an outbreak investigation was opened for people infected with a specific variant of Salmonella Typhimurium ST 36. In August and September, 35 people from 11 different regions became ill.
Information on possible sources of contamination was collected through interviews, questionnaires and purchase receipts from cases, but this did not identify which foods caused illness. Officials believed that the source of the infection was likely a food product with a limited shelf life that was no longer on the market.
The study was closed, but has now been restarted and expanded as several new variants of sequence type 36 have been identified.
Because Salmonella Typhimurium ST 36 is uncommon in Sweden and because cases involving isolates belonging to different variants of this type have been discovered in the same period, officials believe that the outbreak is caused by a common source of infection.
The age of patients ranges from younger than 1 to 89 years, and the median is 44 years. Most patients are in the age groups younger than 1 to 10 years and from 40 to 50 years. More women than men are sick.
An investigation is underway involving regional infection control, municipalities, the Swedish Food Agency (Livsmedelsverket) and the Swedish Public Health Agency.
This includes collecting information about which cases ate before becoming ill. The answers are compared with what people in a healthy comparison group say they ate to assess whether there are foods that outbreak patients ate in greater quantities than expected.
Officials have also alerted EU networks to try to track any possible spread of Salmonella Typhimurium ST 36 in other European countries.
Salmonella egg incident
Folkhälsomyndigheten is also part of a team investigating a new Salmonella outbreak possibly linked to imported eggs.
Since the beginning of the year, there have been several reports of people infected with Salmonella Enteritidis, and epidemiological research has identified the consumption of raw or lightly cooked eggs in various dishes as a likely source. The first patients became infected between late 2023 and early 2024, but most cases have onset from July to September.
Several outbreak strains appear to be involved. The number of people who become ill from each of the suspected strains varies. Patients come from all age groups and there is no unusual gender distribution. So far, about 80 people have fallen ill from infections linked to eggs from Ukraine.
Eggs have been sold through wholesalers to stores that do not belong to the larger chains and to restaurants. Several patients have consumed soft-boiled or unheated eggs in products such as mayonnaise, béarnaise sauce and pasta carbonara. Salmonella was not detected when eggs from shops and restaurants were tested.
Livsmedelsverket recommends not eating raw eggs from countries other than Sweden, Norway, Finland and Denmark. There is a greater risk that eggs from places outside the Scandinavian countries contain Salmonella. Information about the origin of eggs can be found on the packaging and on a stamp on each egg.
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