Outbreaks of norovirus in Sweden linked to shrimp from Estonia may have affected about 100 people.

Reports from local authorities have not been fully compiled yet but based on preliminary information officials believe more than 100 people have fallen sick.

It is mostly local outbreaks at workplaces wher people have eaten shrimp sandwiches or a popular product in Scandinavia called “smörgåstårta.” This food, also called a sandwich cake, looks like a cake but instead of sponge uses bread and often includes cheese, vegetables, cold meats and fish.

Peeled shrimps in brine from the implicated batch were mostly distributed within one region which was named by local media as Varnamo in Jönköping County in southern Sweden.

Outbreak investigation
The outbreak began on the last weekend of February. The implicated batch was withdrawn from the market on March 1 when the distributing company received information about the first illnesses.

Mats Lindblad, from Livsmedelsverket (the Swedish Food Agency), said the link was made by patient interviews with product testing results pending.

“So far it’s based on interviews with cases and backwards and forward tracing of food. Results from product testing are still pending, but samples of shrimps from the implicated batch have been sent to the Swedish Food Agency for microbiological analysis of norovirus,” he said.

“The product has only been sold to food business operators producing shrimp sandwiches or smörgåstårta. Therefore, no public recall has been deemed necessary.”

Lindblad said because of the limited distribution and withdrawal measures more illnesses are not expected.

The most common symptoms of norovirus are diarrhea, vomiting, nausea and stomach pain. Other symptoms may include low-grade fever, headache, chills, muscle aches and a sense of tiredness.

A person usually develops symptoms 12 to 48 hours after being exposed to norovirus. Most people with illness get better within one to three days. People who are ill should drink plenty of liquids to replac lost body fluids and prevent dehydration.

Norovirus is transmitted by having contaminated food or water or from person to person through contact with the skin, objects or inhaling airborne particles.