Surveillance of pelagic birds for influenza A viruses.

Within a 4-year surveillance period for influenza A virus in pelagic birds, 351 influenza A strains were isolated from the trachea or cloaca of 3344 apparently healthy ducks, gulls, swans, terns and geese. The isolated influenza A viruses represent 14 subtypes. Their haemagglutinins (HA) were mainly related to avian HA, but also to the human HA H2 and to the swine HA Hswl. The neuraminidases (NA) were identified as avian, equine and human NA. The isolated influenza A strains include fowl plague-like viruses Havl Neql, strains with the surface antigen Hswl Nav4 and the subtype Hav7 Navl isolated from unconcentrated water samples. A subtype unknown to date, with the antigen formula H2 Nav4, was isolated from ducks. 8.2% of pekin ducks showed dual infections.