Fig 1 Timeline of HPAI H5N1 evolution. This timeline shows significant events and important clades of HPAI H5N1.
#18,474
Anyone who has suffered through some of my longer - and often tortuous - rambles about the evolution and spread of HPAI H5Nx knows that there are significant gaps in our knowledge, and a good deal of uncertainly on its future course and impact.
Since these viruses continue to diversify and evolve, new - and sometimes contradictory - information emerges practically every week. Keeping up isn't easy.
Aiding in that, we've got a minireview today which does an excellent job of summarizing the knowns, unknowns, and challenges surrounding the clade 2.3.4.4b H5N1 virus.
While currently our biggest concern, this subtype/clade is only a subset of a larger constellation of highly mutable HPAI H5 viruses (e.g. H5N6, H5N5, clade 2.3.2.1a in India and 2.3.2.1c in Cambodia, etc.) around the globe.
I've only reproduced the abstract and some brief excerpts. Follow the link to read it in its entirety.
Highly recommended.
Clade 2.3.4.4b highly pathogenic avian influenza H5N1 viruses: knowns, unknowns, and challenges
Authors: Zimin Xie, Jiayun Yang, Wanlin Jiao, Xueqing Li, Munir Iqbal , Ming Liao https://orcid.org/0000-0001-8731-4528 mliao@scau.edu.cn, Manman Dai
https://doi.org/10.1128/jvi.00424-25
ABSTRACT
Since 2020, the clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 viruses have caused unprecedented outbreaks in wild birds and domestic poultry globally, resulting in significant ecological damage and economic losses due to the disease and enforced stamp-out control. In addition to the avian hosts, the H5N1 viruses have expanded their host range to infect many mammalian species, potentially increasing the zoonotic risk.
Here, we review the current knowns and unknowns of clade 2.3.4.4b HPAI H5N1 viruses, and we highlight common challenges in prevention. By integrating our knowledge of viral evolution and ecology, we aim to identify discrepancies and knowledge gaps for a more comprehensive understanding of the virus. Ultimately, this review will serve as a theoretical foundation for researchers involved in related avian influenza virus studies, aiding in improved control and prevention of H5N1 viruses.
INTRODUCTION
Influenza A viruses (IAVs) are important zoonotic pathogens, posing a credible concern to animals and humans. The viral genome is negative-sense, single-stranded, and consists of eight segments. IAVs are classified into 19 hemagglutinin (HA) subtypes and 11 neuraminidase (NA) subtypes (1). H17N10 and H18N11 have only been identified in bats, while H1–H16, H19, and N1–N9 can infect a wide range of avian and mammalian hosts, including humans (2, 3). Wild birds are the natural reservoirs for IAV, where they are referred to as avian influenza viruses (AIVs). All 16 HA subtypes and 9 NA subtypes have been identified in wild birds (4).
Since 2020, many countries have reported outbreaks of clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 viruses, leading to devastating economic losses (5–9). Domestic birds, like chickens, typically experience a 100% mortality rate following infection with H5 HPAIVs. Wild birds, on the contrary, are naturally resistant to HPAIVs, exhibiting no or mild clinical symptoms upon HPAIV infection (10, 11).
However, the contemporary clade 2.3.4.4b H5N1 viruses have caused unprecedented infections in wild bird populations with high mortality rates (5, 12–14). In addition to avian species, many countries have reported the infections of clade 2.3.4.4b H5N1 virus in mammalian species including foxes, domestic cats, minks, sea lions, and most recently in dairy cows (7, 9, 13, 15–17). Moreover, sporadic zoonotic infections have been reported in several countries (18–20).
Altogether, this suggests that the current clade 2.3.4.4b HPAI H5N1 viruses pose significant threats to human and animal health. The review delves into published data of clade 2.3.4.4b H5N1 HPAIVs. We will also shed light on the current situation of the virus and highlight potential avenues for future research.
(SNIP)
CONCLUDING REMARKS
