High prevalence of influenza A virus in ducks caught during spring migration through Sweden

As part of our ongoing screening of wild birds in Northern Europe, 358 mallards (Anas platyrhynchos) and 203 shelducks (Tadorna tadorna) were caught in southern Sweden during the spring 2003. Faecal samples were analyzed by real time RT-PCR for the presence of influenza A virus. In contrast to what has been found in North American studies; Eurasian spring migrating ducks passing through Sweden had a relatively high prevalence of influenza A virus.