Skip to content
Review Open access

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

Sep 2026 · Acta Medica Bulgarica · Vol 53, pp. 75 - 82 · 0 citations · 57 references

TL;DR

A literature search focusing on reported infections amona humans with Highly Pathogenic Avian Influenza (HPAI) and all reported H5Nx and other zoonotic subtypes was performed, but was expanded to all reported H5Nx and other zoonotic subtypes when clade-specific data were sparse.

Abstract

Abstract 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.

Read PDF

Similar papers

Open access Sep 2026

Experimental Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Alpacas, 2026

Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b virus continues to spread globally and sporadically transmits from avian reservoirs to mammalian hosts. In May 2024, H5N1 infections in young goats and alpacas in the United States were reported. Nevertheless, the overall susceptibility of camelids to clad...

Jacob Schön, A. Breithaupt, N. Halwe et al. · 0 citations
Open access Aug 2026

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

The report highlights the genetic and antigenic features of a clade 2.3.4b HPAI H5N1 virus isolated from a free-range layer duck in the Kuttanad delta of Kerala, India, in 2022, suggesting a role for these birds in its introduction.

K. Gaurav, Manoj Kumar, S. Nagarajan et al. · 0 citations
Open access Sep 2026

First detection of High pathogenicity Avian Influenza A(H5N1) Clade 2.3.4.4b Genotype EA-2024-DI.2.1 in Egypt associated with migratory wild birds

Findings provide evidence for the introduction of EA-2024-DI.2.4.1 into Egypt through migratory wild birds and highlight the importance of continued genomic surveillance at the wild bird domestic poultry interface and antigenic evaluation against vaccines currently used in Egypt.

N. Hagag, Amany Adel, Mostafa R. Zaher et al. · 0 citations
Open access Sep 2026

Highly Pathogenic Avian Influenza Viruses H5N1 and H5N5 in Red Foxes (Vulpes vulpes) in Norway during 2022-2024

Since 2020, highly pathogenic avian influenza (HPAI) A(H5Nx) clade 2.3.4.4b viruses have spread globally, causing extensive outbreaks in domestic and wild birds. Increased circulation has resulted in frequent spillover to mammals, and occasional mammal-to-mammal transmission. Although human infections remain rare, the...

M. R. Reiten, C. A. Bøe, Line Olsen et al. · 0 citations
Open access Oct 2026

Multiple introductions and spread of novel reassortant highly pathogenic avian influenza A (H5N1) clade 2.3.4.4b viruses via wild birds, South Korea, 2024–2025

Between 14 October 2024 and 24 March 2025, 43 cases of clade 2.3.4.4b highly pathogenic avian influenza (HPAI) type A (H5N1) infections in wild birds and 1 case in a leopard cat were detected through the national HPAI surveillance program. We performed whole-genome sequencing of 51 isolates and investigated their phylo...

Ye-Ram Seo, Ha-Eun Lee, Dong-ju Kim et al. · 0 citations
Open access Aug 2026

Enhanced Pathogenicity and Contact Transmissibility of Human-origin Avian Influenza H5N1 Clade 2.3.4.4b Genotype B3.13 Compared to D1.1 in Ferrets

Using the ferret model of influenza infection and transmission, it is demonstrated that the currently circulating B3.3.13 is already well adapted for mammalian infection and transmission whereas D1.1 rapidly acquires mammalian-adaptive mutations after a single infection and/or transmission event, highlighting its evolu...

Ahmed M. Elsayed, Ramya S. Barre, Mahmoud Bayoumi et al. · 0 citations

We use cookies to run the site and, with your consent, for analytics and to show ads. See our Cookie Policy.