Occurrence of norovirus and hepatitis A virus in shellfish

Norovirus (NoV) and hepatitis A virus (HAV) are a common cause of gastroenteritis outbreaks associated with consumption of raw shellfish. The majority of NoV infections worldwide are due to geno group II NoVs. The predominant HAV strains belong to sub -genotype IB. A total of 369 bivalve molluscs (294 mussels, 42 clams and 33 oysters) from several retail points and harvesting class -A areas of the Adriatic basin in South Italy, North Italy and Albania (Butrinti Lagoon) were sampled between 2008-2013. All the samples were screened by a hemi-nested RT-PCR specific for NoV geno group II and by a nested RT-PCR for the VP1/2A region of HAV. NoV RNA was detected in 10,5% of samples and ranged from 3% in 2008 to 85% in 2013. HAV RNA was detected in 32,5% of samples and ranged from 90% in 2008 to 3,1% in 2013. The marked decrease in HAV prevalence may be the related to the vaccine-induced immunity, able to interrupt the ecological cycle of HAV. Monitoring the epidemiology of the virus strains circulating in the field is pivotal to develop and assess the efficacy of new control strategies to reduce the risks for public healt