A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
Twenty-four patients in the Netherlands who became ill during November 2024–February 2025 were part of a hepatitis A virus genotype IA cluster. Consumption data combined with detection of RNA of the hepatitis A outbreak strain in a food product pointed toward frozen blueberries from a specific supermarket chain as the source.
Hepatitis A is an acute, self-limiting liver disease transmitted primarily via the fecal–oral route. Risk factors for infection include consumption of contaminated food or water and person-to-person contact. In Western Europe, hepatitis A endemicity is low ( 1 ) and is associated primarily with travel to endemic countries ( 2 ) or consumption of contaminated, imported food ( 3 ).
In foodborne outbreaks, investigators often use questionnaires to link patients based on consumption of a specific food product and employ genotyping to identify genetically related cases. On December 31, 2024, public health officials in the Netherlands identified a third case of hepatitis A with a specific genotype IA strain, referred to as the outbreak strain. One week later, the cluster expanded to 9 cases, and all case-patients reported consumption of frozen fruits bought from 1 specific supermarket chain, triggering an outbreak investigation.
Hepatitis A is a notifiable disease in the Netherlands. Accordingly, regional Public Health Services must collect relevant patient data and report them, pseudonymized, to the National Institute of Public Health and the Environment ( 4 ). As part of the molecular surveillance of hepatitis A virus (HAV), the agency also requests laboratories to send HAV-positive serum and stool samples for further testing, including sequencing according to the HAVNET typing protocol ( 5 ). For the outbreak we report, we defined an outbreak case as a person infected by an IA strain of hepatitis A sharing at least 459/460 nt with the outbreak strain and a disease onset from November 2024 onward. This outbreak investigation was conducted as part of routine public health surveillance and so was exempt from ethical approval. We submitted 2 representative sequences of nearly complete genomes to GenBank (accession nos. PZ095824 and PZ095825).
In addition to conducting standard interviews with notified outbreak case-patients, 24 in total, we also developed and administered a questionnaire featuring advertisement pictures of all packaged frozen fruits sold by the suspected supermarket chain, following previous methods ( 6 ). We were unable to collect food consumption data for 1 patient and determined another patient to be likely infected through person-to-person contact with another outbreak case-patient. We determined that the remaining 22 patients had consumed a specific brand of frozen fruit purchased at the same supermarket chain. Nineteen patients reported consuming frozen blueberries, 14 of which identified a specific package. The remaining 3 of the 22 patients reported consuming bilberries, blackberries, or a mix that also contained blueberries, but those patients were not available for further questioning about specific consumption of blueberries.
Food safety inspectors collected l…