.JPG)
V.J. Munster, T.M. Bestebroer, S. Herfst, L. van der Kemp, G.F. Rimmelzwaan,
A.D.M.E. Osterhaus and R.A.M. FouchierInstitute of Virology, Erasmus Medical Centre, The Netherlands. P.O Box 1738, 3000 DR Rotterdam, The Netherlands
Wild birds, in particular waterfowl (Anseriformes and Charadriiformes) represent the natural reservoir of avian influenza A viruses. Using rapid high-throughput PCR-based screening methods and a large network of ornithologists, we have screened more than 15000 wild birds in Northern Europe. Although our primary focus was on ducks, geese and gulls, we have also tested thousands of samples from other species including passerines, birds of prey, and penguins. Overall, approximately 1% of our samples was found to be PCR positive for influenza A virus. All positive samples were obtained from ducks (mallard, teal, wigeon, shoveler), geese (greylag, white-fronted), black-headed gulls and guillemots. A wide variety of isolates were obtained representing HA subtypes 1, 2, 3, 4, 5, 7, 10, 11 and 13. From black-headed gulls in Sweden and The Netherlands, we isolated H13 viruses as well as viruses that could not be typed with our reference reagents. These viruses are closely related to the gull viruses of subtype H13, but may represent a novel HA subtype, H16. We also isolated a low pathogenic avian influenza (LPAI) H7, which was closely related to virus isolates of the current H7N7 highly pathogenic avian influenza (HPAI) outbreak in commercial poultry farms in The Netherlands, Belgium and Germany. This indicates an introduction of low pathogenic avian H7N7 influenza virus into poultry. This and other outbreaks (H5N1, Hong Kong) have increased the awareness of the pandemic threat of avian influenza A viruses.
