An avian influenza virus of H10 subtype that is highly pathogenic for chickens, but lacks multiple basic amino acids at the haemagglutinin cleavage site

Avian influenza virus isolate A/mandarin duck/Singapore/805/F-72/7/93 was found to be consistently highly pathogenic by recognised in vivo testing procedures although it was of a subtype (H10) not usually associated with high pathogenicity. The virus was also not typical of highly pathogenic influenza viruses in that it was not pathogenic when administered intra-nasally, did not possess a haemagglutinin cleavage site with multiple basic amino acids and did not replicate in the brains of chickens after intravenous inoculation. A re-examination of the earlier H10 isolate A/turkey/England/384/79 suggested that it was similarly pathogenic. The pathogenicity may have been associated with replication in the kidney.