Officials in Sweden and Denmark are investigating a hepatitis A outbreak with frozen imported berries suspected to be the source of infection.

Since mid-July, nine patients with the same type of hepatitis A virus have been reported from five different regions in Sweden. The latest patient fell ill on Sept. 18.

Six women and three men from Norrbotten, Västra Götaland, Stockholm, Uppsala and Södermanland are infected with the liver virus. Patients range from 2 to 78 years old. Also, a couple of people are ill in Denmark.

Frozen berries named as potential source
Interviews have found some people ate frozen imported berries, especially raspberries, which were not heated before consumption. However, analysis of sampled berries has not been able to detect the hepatitis A virus.

Local infection control units, Swedish Food Agency (Livsmedelsverket), and Public Health Agency of Sweden (Folkhälsomyndigheten) are investigating to confirm the source of the infections.

Two Danish cases have been linked to the Swedish outbreak and a cross-border investigation has been initiated.

Different Denmark outbreak
This outbreak is not believed to be connected to another previously reported outbreak of hepatitis A in Denmark. The type of hepatitis A virus behind the Swedish outbreak and two Danish cases is genotype IA while the one responsible for the other illnesses in Denmark is 1B.

In Denmark, the domestic outbreak investigation is ongoing with no firm hypothesis on the source. It includes 16 patients aged 17 to 63. Eleven people have needed hospital treatment. Interviews have shown patients have not been traveling, do not know each other, and had not participated in joint events.

European authorities investigated more than 60 hepatitis A cases in eight countries in 2018 but did not find a source. People in Denmark, France, Germany, Ireland, Netherlands, Spain, Sweden and the United Kingdom were infected with one of two Hepatitis A virus genotype IA strains.

Hepatitis A is spread when someone ingests the virus through close contact with an infected person or by eating contaminated food or drink. The incubation period is usually 14 to 28 days. Symptoms can last up to two months and include fatigue, nausea, stomach pain, and jaundice. Most people do not have long-lasting illness. The best way to prevent it is to get vaccinated.