The impact of viral molecular diversity on the clinical presentation and outcome of acute hepatitis B in Italy.

The incidence of acute hepatitis B (AHB) in Italy, mostly sustained by hepatitis B virus (HBV) genotype D, has significantly decreased in the last two decades, but the new HBV strains introduced through immigrant populations from countries with a higher endemicity constitute a new emergency. HBV-genotype D still predominates in AHB, the subgenotype D3 being associated with parenteral transmission, and the recently emerging subgenotype A2 with unsafe sexual intercourse. Genetic, phylogenetic and evolutional analyses are powerful tools for countries with high immigration rates to monitor new viral strains with different aggressiveness and a different response to therapy.