Highly pathogenic avian influenza A(H5N1), clade 2.3.2.1a, with an H9-like polymerase basic protein 1 gene, isolated in Bhutan in 2012, replicated faster in vitro than its H5N1 parental genotype and was transmitted more efficiently in a chicken model. These properties likely help limit/eradicate outbreaks, combined with strict control measures.
Keywords: Bhutan; Indian subcontinent; avian influenza; clade 2.3.2.1a; ferret model: respiratory diseases; highly pathogenic avian influenza H5N1; influenza; influenza virus; outbreak; reassortant; transmission; viruses; zoonoses.