Main conclusions and recommendations
Between 1 October 2012 and 8 April 2013, 16 confirmed cases of hepatitis A virus (HAV) infections with subgenotype IB and identical RNA sequence were reported in four Nordic countries.
As none of the cases have a travel history outside the EU within their period of potential exposure, this represents a multicountry outbreak, with exposure currently taking place in the EU. The descriptive epidemiology indicates foodborne transmission originating from a persistent common source in the EU with possibly multiple vehicles of infection that are contaminated with viruses sharing an identical sequence.
Epidemiological investigations in affected countries strongly point towards frozen berries as the vehicle of infection. This hypothesis is being further investigated. RNA sequencing, interviews of cases in affected countries, food investigations, and purchase history research should provide additional evidence.
According to the available information, it is likely that additional cases will be identified and reported. ECDC encourages Member States to raise awareness about a possible increase in HAV subgenotype IB cases, report all new cases in EPIS-FWD, and use the common epidemic case definition and questionnaire to interview recent cases (available in EPIS-FWD and upon request).
ECDC, EFSA and the European Commission, in cooperation with the affected countries, will continue to closely monitor this event and will update this outbreak assessment as soon as new relevant information becomes available.