Genetic Diversity of Highly Pathogenic Avian Influenza H5N1 Clade 2.3.4.4b Detected in Pennsylvania Poultry During 2022 Disease Outbreak. Highly Pathogenic Avian Influenza A

The 2022 highly pathogenic avian influenza (HPAI) outbreak of H5N1 clade 2.3.4.4b is one of the major avian influenza outbreaks, leading to multiple spillover events infecting domestic and wild bird flocks, as well as mammals. The sustained spread is result of the viral circulation in wild birds across migratory flyways in North America. Pennsylvania has a significant poultry population that supports the retail and live bird markets. The state also features migratory bird stopovers in Atlantic flyway, increasing poultry susceptibility for HPAI infections. This study investigates the infection and sequence data of H5N1 clade 2.3.4.4b during the 2022 outbreak in Pennsylvania. Eight different IAV genotypes were detected(A1, B1.1, B1.3, B1.2, B2.2, B3.3, B3.5, and minor24). The earliest detection was of genotype A1 in commercial poultry in April 2022, followed much later by the genotype B3.3 in backyard flocks. Genetic analysis of B3.3 sequences showed the genotype had PB1 and PB2 genes clustering with low pathogenic avian influenza sequences collected from wild birds, suggesting potential genetic recombination. This study sheds light on the genetic diversity of H5N1 during the 2022 outbreak in Pennsylvania poultry, contributing to the understanding of the viral evolution and its potential impacts on animal and public health.