A new avian influenza virus from feral birds in the USSR: recombination in nature?

Six avian influenza A viruses isolated in the USSR were characterized antigenically by using specific antisera to the isolated surface subunits of the known reference strains. Three of the viruses, all isolated from the same region, were characterized as A/duck/Ukraine/63 (Hav7 Neq2), and a virus isolated from a crow was of the Hong Kong/68 (H3 N2) type. The remaining two viruses were novel in that they possessed Hav7 Nav2 antigens, a combination that has not previously been reported. It is suggested that these new influenza viruses might have arisen by recombination in nature between the A/duck/Ukraine/63 (Hav7 Neq2) and A/tern/So. Africa/61 (Hav5 Nav2) strains of avian influenza viruses.