An investigation into a Salmonella outbreak in Sweden has been restarted after more people fell sick.
From August to October, 81 people from 18 regions contracted Salmonella Typhimurium with sequence type (ST) 36. Where information about the country of infection is available, all cases were infected in Sweden.
Folkhälsomyndigheten (the Public Health Agency of Sweden) reported that patients are infected with one of about 10 different but genetically related bacterial variants that have caused illness.
Further cases after initial work
In 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 about possible sources of infection was collected via interviews, questionnaires, and purchase receipts from cases, but this did not identify what food caused illnesses. Officials believed the source of infection was likely a food item with a limited shelf life that was no longer on the market.
The investigation was closed but has now been restarted and broadened as several new variants of sequence type 36 have been identified.
Since Salmonella Typhimurium ST 36 is unusual in Sweden and because cases with isolates belonging to different variants of this type have been detected during the same period, officials believe that a common source of infection causes the outbreak.
Patients range in age from less than 1 to 89, and the median is 44. Most are in the age groups less than 1 to 10 and 40 to 50. More women than men are sick.
An investigation involving regional infection control, municipalities, the Swedish Food Agency (Livsmedelsverket), and the Public Health Agency of Sweden is ongoing.
This includes gathering information about what cases have eaten before becoming ill. Answers are compared to what people in a healthy comparison group say they have eaten to assess whether there are foods that outbreak patients have eaten to a greater extent than expected.
Officials have also alerted EU networks to try and detect any possible spread of Salmonella Typhimurium ST 36 in other European countries.
Salmonella egg incident
Folkhälsomyndigheten is also part of a team looking into another Salmonella outbreak with a probable connection to imported eggs.
Since the beginning of the year, several reports of people infected with Salmonella Enteritidis have been identified, and epidemiological investigations have indicated that the consumption of raw or lightly cooked eggs in various dishes is a likely source. The first patients were infected from late 2023 to early 2024, but most cases have illness onset dates from July to September.
Several different outbreak strains appear to be involved. The number of people sickened by each of the suspected strains varies. Patients are from all age groups, and there is no unusual gender distribution. About 80 people have so far fallen ill with infections linked to eggs from Ukraine.
Eggs have been sold to shops that do not belong to the larger chains and to restaurants via wholesalers. Several patients have consumed soft-boiled or unheated eggs in items such as mayonnaise, Béarnaise sauce, and pasta carbonara. Testing of eggs from shops and restaurants has not detected Salmonella.
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 Nordic nations contain Salmonella. Information about the origin of eggs should be found on the packaging and on a stamp on each egg.
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