Clinical and Mutagenic Spectrum of Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4B: A Narrative Review

Avian influenza A(H5N1) is a highly pathogenic virus causing significant out-breaks in birds and sporadic human infections since 1997. The virus is classified into various clades based on genetic characteristics, and recently, concerns have been raised over the risk ofclade 2.3.4.4b becoming widespread and infecting humans. Since 1997, more than 1,000 infections with highly pathogenic avian influenza A(H5N1) virus among humans have been reported globally. Given ongoing A(H5N1) outbreaks in animals, understanding the frequency of A(H5N 1) virus infections ‘among asymptomatic persons can inform public health risk assessments and infection prevention guidance. We performed a literature search focusing on reported infections amona humans with Highly Pathogenic Avian Influenza (HPAI). This study was conceived as a narrative review focusing on clade 2.3.4.4b H5N1, but was expanded to all reported H5Nx and other zoonotic subtypes (H5N6, H6N1, H7N9, H10N3) when clade-specific data were sparse. Although not a formal systematic review, the search, screening, and appraisal followed the PRISMA 2020 Checklist for search reporting where applicable.