Gene segment reassortment between Eurasian and American clades of avian influenza virus in Italy.

All genes of avian influenza A viruses are phylogenetically distinguished into two large clades, namely the American and Eurasian clade. Reassortments among the gene segments of influenza viruses belonging to the two distinct clades are rare events and have never been described in poultry in Europe and Asia before. This study presents the genetic characterization of two influenza viruses isolated from domestic mallards in Italy in 2004 and 2005. Phylogenetic analysis of the entire genome showed that these viruses contain mixed gene segments belonging to the American and Eurasian clades.