Genetic and Antigenic Characterization of a Clade 2.3.4.4b Highly Pathogenic H5N1 Avian Influenza Virus Isolated from a Free-Range Layer Duck in India

Abstract

Highly pathogenic avian influenza (HPAI) H5N1 virus poses a significant threat to the global poultry sector. The report highlights the genetic and antigenic features of a clade 2.3.4.4b HPAI H5N1 virus isolated from a free-range layer duck in the Kuttanad delta of Kerala, India, in 2022. The virus is similar to an H5N1 virus detected in Russia in October 2021 and antigenically distinct from clade 2.3.2, showing a 16-fold reduction in hemagglutination inhibition titer and 23.95% amino acid differences at the HA antigenic sites. The duck virus shares genetic similarities with H5N1 viruses found in Eurasian wild birds, suggesting a role for these birds in its introduction. The study underscores the importance of strengthening avian influenza surveillance to monitor virus evolution and spread.