Isolation of influenza a viruses from commercial ducks on a farm in Norfolk between August 1979 and March 1980.

Investigation of respiratory disease and high mortality which occurred on a commercial duck fattening farm between August 1979 and March 1980 resulted in the isolation of 10 influenza A viruses. The viruses were characterised as Hav6 N2 (three isolates), Hav4 Navl (four isolates), Hav4 Nl (two isolates) and Hav7 Neq2 (one isolate) subtypes by haemagglutination-inhibition and neuraminidase-inhibition tests. A Newcastle disease virus isolate was also obtained from the ducks. All isolates had low intravenous pathogenicity indices in 6-week-old chickens.