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In March 2014, after an increase of notifications of domestically acquired hepatitis A virus infections, an outbreak investigation was launched in Norway. Sequenced-based typing results showed that these cases were associated with a strain that was identical to one causing an ongoing multinational outbreak in Europe linked to frozen mixed berries. Thirty-three confirmed cases with the outbreak strain were notified in Norway from November 2013 to June 2014. Epidemiological evidence and trace-back investigations linked the outbreak to the consumption of a berry mix cake. Identification of the hepatitis A virus outbreak strain in berries from one of the implicated cakes confirmed the cake to be the source. Subsequently, a cluster in Germany linked to the cake was also identified.

In May 2014, a cluster of Yersinia enterocolitica (YE) O9 infections was reported from a military base in northern Norway. Concurrently, an increase in YE infections in civilians was observed in the Norwegian Surveillance System for Communicable Diseases. We investigated to ascertain the extent of the outbreak and identify the source in order to implement control measures. A case was defined as a person with laboratory-confirmed YE O9 infection with the outbreak multilocus variable-number tandem repeat analysis (MLVA)-profile (5-6-9-8-9-9). We conducted a case–control study in the military setting and calculated odds ratios (OR) using logistic regression. Traceback investigations were conducted to identify common suppliers and products in commercial kitchens frequented by cases. By 28 May, we identified 133 cases, of which 117 were linked to four military bases and 16 were civilians from geographically dispersed counties. Among foods consumed by cases, multivariable analysis pointed to mixed salad as a potential source of illness (OR 10.26; 95% confidence interval (CI): 0.85–123.57). The four military bases and cafeterias visited by 14/16 civilian cases received iceberg lettuce or radicchio rosso from the same supplier. Secondary transmission cannot be eliminated as a source of infection in the military camps. The most likely source of the outbreak was salad mix containing imported radicchio rosso, due to its long shelf life. This outbreak is a reminder that fresh produce should not be discounted as a vehicle in prolonged outbreaks and that improvements are still required in the production and processing of fresh salad products.

On 7 March 2014, an increase in hepatitis A virus (HAV) infections was identified in Norway. As of 12 April, 19 cases of HAV infection with a virus strain identical to an ongoing European outbreak have been identified. Six probable cases are currently under investigation. On 11 April, a frozen berry mix cake imported from another European country was found as the likely source of the outbreak; the importer has withdrawn the product in Norway.