Four of the Nordic countries (Denmark, Sweden, Finland and Norway) have detected more hepatitis A cases than usual among people who did not travel abroad during the incubation period before they became ill (domestic infection). Frozen berries may be the source of infection.
Most of the cases are reported in Denmark. The Danish epidemiological investigation showed that frozen berries were the likely source of infection for the outbreak there.
Since October 2012, the Norwegian Institute of Public Health has been notified of 14 domestically-acquired cases of hepatitis A, which is more than expected.
The Institute has collaborated with local municipal medical officers and the Norwegian Food Safety Authority to identify any common sources of infection for the Norwegian cases. The results of this investigation provide no evidence of a common infection source among patients in Norway. Geonotyping of the hepatitis A virus (HAV) isolated from the patients shows that they are infected with several different strains.
Possible common source in the Nordic countries
Sequence analysis of the virus showed that one of the Norwegian cases was infected with the same type of HAV found in Denmark. Some patients in Sweden and Finland also have the Danish outbreak strain.
In collaboration with other national governments and the European Centre for Disease Prevention and Control, the Norwegian Institute of Public Health and the Food Safety Authority are investigating if there are common factors for patients in Norway, Denmark, Sweden and Finland.
The Nordic investigation is mapping what each patient has eaten and whether these products are sold in all four countries. This involves virus analysis, interviewing new patients, food sampling and gathering information about purchased food.
Advice to the public
Sick people excrete the virus in faeces and can infect others through contaminated hands or food and water. The most important measure to prevent transmission to others is good hand hygiene after using the toilet and before eating or preparing food. Infection can also occur from oral sex and oral-anal contact, or through sharing syringes.
People who have been in close contact with individuals with diagnosed hepatitis A should be offered immunoglobulin and / or a vaccine to prevent developing the disease.
Freezing berries does not kill bacteria, viruses and parasites. Many pathogenic microorganisms survive well in frozen products, including hepatitis A.
Hepatitis A virus can come into contact with berries through unhygienic handling during harvesting or from contaminated irrigation water. The virus is killed by heat treatment so to reduce the risk of infection, frozen berries can be boiled for 1 minute before they are used in dishes that will not be heat-treated.
Facts about hepatitis A
- Most people who get hepatitis A are infected abroad.
- The incidence of hepatitis A is particularly high in Africa, South America, the Middle East and much of Asia.
- A high proportion of the population in these countries are infected without symptoms in early childhood.
- Hepatitis A is a virus that can cause liver inflammation, but patients usually recover completely without liver damage.
- Symptoms of hepatitis include fever, nausea, vomiting, abdominal pain and jaundice. Urine becomes dark coloured, and the stools become light.
- Most adults can have symptoms for one or more weeks before they get rid of the infection and become immune. Children may display milder symptoms.
- Patients with hepatitis symptoms should consult a doctor for a correct diagnosis.