Acute hepatitis A in Italy : incidence, risk factors and preventive measures

The incidence of, and risk factors for, acute hepatitis A (AHA) were assessed by using data collected from the Italian surveillance system of acute viral hepatitis (SEIEVA). To this end, a case-control study within a population-based surveillance for acute viral hepatitis was performed. AHA incidence has been estimated since 1991; the association with considered risk factors was analysed from 2001 to 2006 employing cases of acute hepatitis B (AHB) as controls. The incidence of AHA declined from 4 / 100 000 in 1991 to 1.4/100 000 in 2006, with a peak during 1996-1998 due to an outbreak in southern Italy. The incidence of AHA was highest among persons aged 15-24 years. The case-fatality rate was 2.9 / 10 000. Contact with individuals with AHA [adjusted OR (OR(adj)) = 3.8, 95% CI 2.7-5.5; population-attributable risk (PAR) = 7.5%], travelling to endemic areas (OR(adj) = 3.1, 95% CI = 2.6-3.8; PAR = 19.5%), ingestion of raw shellfish (OR(adj) = 1.8, 95% CI = 1.6-2.1; PAR = 26.6%), and cohabitation with day care children (OR(adj) = 1.3, 95% CI = 1.01-1.7; PAR = 2.3%) were the main important risk factors. In 2003, an outbreak, with high case-fatality rate occurred among intravenous drug users, in a central Italian town. A weak association was found for male homosexuality when acute hepatitis C cases were employed as controls (OR(adj) = 1.4 CI, 95% CI = 1.1-1.9). Hepatitis A virus infections are currently occurring more frequently in adults, in whom the disease is most severe. In conclusion, looking at the attributable risks, at present most of the AHA infections are due to shellfish consumption, travel to endemic areas and contact with patients with AHA. Vaccination of individuals at increased risk of infection, as well as persons with underling liver disease and those at increased risk of complications, combined with surveillance of shellfish retail outlets are efficient control measures.