From February to March 2009, H7N6 subtype highly pathogenic avian influenza viruses (HPAIV) were isolated from quails in Aichi Prefecture. The pathogenicity of the virus could be low against chicken because the deduced amino acid sequence at the cleavage site of the hemagglutinin protein was similar to the low pathogenic strain (PKRR). The divergence date of the viruses from the ancestor was estimated to be from March 2002 to July 2004, on the basis of the evolutionary rate among North American type H7 subtype influenza viruses. Because of animal experiments, quails were more susceptible, and the virus was transmitted among quails more efficiently, than chicken and duck. Therefore, H7N6 subtype HPAIV might have been maintained for a certain period among quails since the introduction of the virus.
(Research Team for Zoonotic Diseases)
Uchida Y. et al. (2011) Vet. Microbiol. 147 (1-2): 1-10