Background: In spite of annual vaccination campaigns, hepatitis A cases increased in Catalonia (North-East Spain) in the period 2002-2005 calling for the elucidation of the underlying mechanisms associated to the epidemiological shifts.
Objective: The molecular characterization of the circulating strains to trace their origin and the study of the effects of vaccination on the incidence of sporadic and outbreak-associated cases.
Study design: Forty-eight different hepatitis A virus (HAV) strains isolated from sporadic and outbreaks cases during 2005-2009 in Catalonia were molecularly characterized.
Results: Seventeen out of 48 strains were imported from endemic areas through traveling, immigration and food trade, 12 were endemic strains circulating in the men having sex with men (MSM) group and 1 was from a Roman child. The remaining 18 could not be associated to any specific origin and thus were considered autochthonous. Forty-eight percent of the strains belonged to subgenotype IA, 40% to subgenotype IB and 2% to subgenotype IIIA. The remaining 10% belonged to an undetermined subgenotype equidistant from IA and IB.
Conclusions: During the period 2005-2009, the annual attack rates remained around 3.5 and even increased up to 6.5 in the first half of 2009. This increase with respect to the period 1999-2001, in which vaccination campaigns started to be implemented, is explained by an increase in the number of outbreaks. The predominant subgenotypes were IA and IB. However a considerable amount of strains imported from Peru through consumption of contaminated shellfish belonged to an undeterminded subgenotype that may constitute a new candidate subgenotype IC.
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