Eleven confirmed and two suspected cases come are reported from four Swedish counties, Skåne, Blekinge, Kalmar and Gävleborg.
Nine women and four men aged 11 to 92 are affected. The most recent person to fall ill had symptoms begin on June 18.
The Public Health Agency of Sweden (Folkhälsomyndigheten), the National Food Agency (Livsmedelsverket) and local authorities are involved in the investigation. They traced the source of Hepatitis A virus (HAV) infection to frozen strawberries from Poland and informed Polish authorities of their findings.
All of the cases had smoothies or a dessert containing frozen imported strawberries that were not heated prior to consumption. The strawberries were not sold directly to consumers.
Analysis of the current lot of strawberries from Poland showed they contain the same type of hepatitis A virus, genotype 1B, that has infected the victims. Livsmedelsverket told Food Safety News that patients ate strawberries in smoothies from a juice bar and unheated strawberries in a dessert in a nursing home.
Frozen strawberries have been sold by a company in Poland to a wholesaler in Sweden. The wholesaler sold them to various caterers and restaurants. A recall is underway, and official say the products might still be on the market.
Skogsmat i Uddeholm AB, a Swedish producer and supplier of berries, fruits, vegetables, mushrooms, purées and juice concentrates, imported the strawberries from Poland. Menigo Foodservice AB, a food supplier based in Sweden and owned by Sysco, distributed them.
Livsmedelsverket said the distributor has not been fined or closed because it did what it was supposed to given the circumstances.
The agency added extra checks of imported strawberries, as a general action, is not an option as it would be a breach of rules concerning the free movement of goods and products in the EU internal market.
Two outbreaks of Hepatitis A infections were noted in the second quarter of this year, according to international food safety statistics, the one referenced above and another linked to frozen pomegranate arils.
Hepatitis A virus is transmitted through ingestion of contaminated food and water or through direct contact with an infectious person, according to the World Health Organization.
Anyone who has not been vaccinated or previously infected can get infected.
The incubation period is usually 14-28 days. Symptoms range from mild to severe and can include fever, malaise, loss of appetite, diarrhoea, nausea, abdominal discomfort, dark-coloured urine and a yellowing of the skin and whites of the eyes.
In contaminated food, the highly contagious liver virus is killed when exposed to temperatures of mire than 185 degrees F (85 degrees C) for one minute, according to the Centers for Disease Control and Prevention.