Influenza A virus surveillance in wild birds in Northern Europe in 1999 and 2000.

Using reverse transcription/polymerase chain reaction (RT-PCR), we have screened more than 8500 wild birds in Northern Europe in 1999 and 2000 for the presence of influenza A virus. Although our primary focus was on ducks, geese, and shorebirds, we have also tested thousands of samples from other bird species. Approximately 1% of our samples were positive for influenza A virus by RT-PCR, and from half of these we were able to isolate influenza A virus in embryonated chicken eggs. A wide variety of isolates was obtained representing hemagglutinin (HA) subtypes 1 through 7, 10, 11, 13, an unidentifiable HA, and neuraminidase (NA) subtypes 1 through 8.