Emergence and Rapid Spread of a New Reassortant High Pathogenicity H5N1 Clade 2.3.4.4b Avian Influenza Virus in Nigeria

Over the past two decades, West Africa has experienced recurrent incursions of Goose/Guangdong-lineage highly pathogenic avian influenza (HPAI) A(H5N1), with Nigeria as a hotspot for repeated introductions and sustained circulation. Since 2021, European-origin clade 2.3.4.4b H5Nx genotypes, particularly EA-2020-C, have predominated in regional poultry. Here, we report the emergence and rapid spread in Nigeria, and West Africa, of a new clade 2.3.4.4b H5N1 genotype, designated EA-2024-DV, marking a major shift in the circulating virus population. These findings underscore the region's ongoing vulnerability to novel introductions and highlight the need for sustained surveillance across migratory bird routes and poultry production networks.