Influenza A virological surveillance in feral waterfowl in Taiwan from 1998 to 2002

Monitoring avian influenza in migrating birds from 1998 to 2002, we sampled 10,945 samples totally for virus isolation, and 232 AI virus isolates were obtained. Further subtyping the isolates, based on hemagglutinin inhibition (HI) and neuraminidase-inhibition (NI) tests, they were classified into 17 different subtypes, i.e., H1N1, H1N3, H2N3, H3N8, H3N6, H4N2, H4N6, H4N7, H4N8, H6N1, H6N2, H7N1, H8N4, H10N4, H10N7, H11N9, and H14N7, respectively. The results revealed that the winter migratory birds carried a lot of AI viruses and the subtype of the isolates bad large antigenic variation, with 10 HA and 7 NA subtypes being recognized. On the other hand, H4N6 virus was the dominant subtype and being isolated more frequently among the isolates. These revealed again that a wide variety of AI subtypes might be found in a country with wild bird population, which were carried into an area each year and might impose a threat on the local poultry industry. (C) 2004 Published by Elsevier B.V.