title: International linkage of two food-borne hepatitis A clusters through traceback of mussels, the Netherlands, 2012.
abstract: This report describes an outbreak investigation starting with two closely related suspected food-borne clusters of Dutch hepatitis A cases, nine primary cases in total, with an unknown source in the Netherlands. The hepatitis A virus (HAV) genotype IA sequences of both clusters were highly similar (459/460 nt) and were not reported earlier. Food questionnaires and a case-control study revealed an association with consumption of mussels. Analysis of mussel supply chains identified the most likely production area. International enquiries led to identification of a cluster of patients near this production area with identical HAV sequences with onsets predating the first Dutch cluster of cases. The most likely source for this cluster was a case who returned from an endemic area in Central America, and a subsequent household cluster from which treated domestic sewage was discharged into the suspected mussel production area. Notably, mussels from this area were also consumed by a separate case in the United Kingdom sharing an identical strain with the second Dutch cluster. In conclusion, a small number of patients in a non-endemic area led to geographically dispersed hepatitis A outbreaks with food as vehicle. This link would have gone unnoticed without sequence analyses and international collaboration.
authors.affiliation: Laboratory for Feed and Food Safety, Food and Consumer Product Safety Authority (NVWA), Wageningen, the Netherlands.
authors.forename: Ingeborg L A
authors.initials: IL
authors.lastname: Boxman
authors.forename: Linda
authors.initials: L
authors.lastname: Verhoef
authors.forename: Harry
authors.initials: H
authors.lastname: Vennema
authors.forename: Siew-Lin
authors.initials: SL
authors.lastname: Ngui
authors.forename: Ingrid H M
authors.initials: IH
authors.lastname: Friesema
authors.forename: Chris
authors.initials: C
authors.lastname: Whiteside
authors.forename: David
authors.initials: D
authors.lastname: Lees
authors.forename: Marion
authors.initials: M
authors.lastname: Koopmans
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D049872:Bivalvia / Q000821:virology*; D016022:Case-Control Studies; D002489:Central America; D002642:Chick Embryo; D002648:Child; D016000:Cluster Analysis; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D016679:Genome, Viral; D005838:Genotype; D006506:Hepatitis A / Q000175:diagnosis / Q000453:epidemiology* / Q000821:virology; D030041:Hepatitis A virus / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009426:Netherlands / Q000453:epidemiology; D010802:Phylogeny; D012367:RNA, Viral / Q000097:blood / Q000235:genetics / Q000302:isolation & purification; D012307:Risk Factors; D017422:Sequence Analysis, DNA; D012758:Shellfish / Q000821:virology*; D014195:Travel; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D012367:RNA, Viral
keywords: Hepatitis A virus; Shellfish; epidemiology; food-borne infections; outbreaks; surveillance