Abstract
This study describes an outbreak investigation of 14 hepatitis A cases in the Netherlands. The hepatitis A virus (HAV) genotype IB sequences in cases were highly similar (459/460 nt). The origin of strains could be narrowed to Bulgaria based on information from EPIS-FWD. As an association with consumption of soft fruit was suspected, a case–control study was initiated using a questionnaire and a list of pictures of soft fruit available at the supermarket chain involved. Twelve out of 13 cases consumed a specific frozen raspberry/blueberry product shown on the list (OR 46.0, 95% CI 5.0–27). In multivariable regression analysis this product was the only risk factor (aOR 26.6, 95% CI 2.0–263). Laboratory analyses could not demonstrate HAV-RNA in batches that had been on the market in the incubation period of patients. Trace back of frozen fruit showed that raspberries had been traded by a producer in Bulgaria. After withdrawal of the product from the supermarket no new cases were reported. Use of advertisement pictures of consumed food was helpful in this investigation. Suspicion of the source was strengthened by data from molecular typing and food trace back activities, underlining the importance of good (inter)national cooperation between public health and food safety organisations.
Highlights
Hepatitis A virus (HAV) is a faecal-orally transmitted pathogen causing acute self-limiting hepatitis
The present study describes the outbreak investigation in which molecular genotyping, a case–control study using a list of food pictures, food analysis, and trace back led to recall of the suspected food product
Combined analyses of data has led to the conclusion that frozen raspberries from Bulgaria were the most likely source for this food-borne hepatitis A virus outbreak
Summary
Hepatitis A virus (HAV) is a faecal-orally transmitted pathogen causing acute self-limiting hepatitis. As a result introduction of HAV-contaminated food in EU/EEA countries may lead to diffuse outbreaks that are geographically and temporally dispersed. Three multinational outbreaks of hepatitis A affecting EU/EEA countries were reported with suspected transmission through soft fruit (Gillesberg Lassen et al 2013; EFSA 2014; Sane et al 2015). Cases are reported in a national electronic registration system for infectious diseases (Osiris) including demographic and epidemiological data (Petrignani et al 2014). 70% of notified hepatitis A cases are sent to the National Institute for Public Health and Environment (RIVM) for genotyping. A national outbreak investigation was initiated when a fourth and fifth case were reported from two different geographical regions and the RIVM showed that all cases had been infected by an identical genotype IB strain (see Fig. 1, timeline)
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