A recent study published in Nature reveals major changes in the ecology and evolution of highly pathogenic avian H5 influenza viruses, including a shift in global distribution. The findings suggest that the epicentre of these viruses has extended beyond Asia to new regions including parts of Africa and Europe.
Highly pathogenic avian H5N1 virus activity has intensified globally since 2021, infecting and killing increasing numbers of wild birds and poultry, as well as posing a risk to mammals (including humans). H5N1 emerged in China in 1996. The scale of H5 outbreaks in wild birds has escalated beyond Asia since 2014, but the origins of recent resurgences and the underlying evolution of these viruses has been unclear.
Dr. Vijaykrishna Dhanasekaran from the University of Hong Kong and others examined the changing origins and trends of highly pathogenic avian H5 outbreaks using epidemiological data collected by the Food and Agricultural Organization and the World Organization for Animal Health between 2005 and 2022, alongside the analysis of more than 10,000 whole viral genomes.
Key resurgent events were identified in 2016/17, with genome analysis revealing that the viral lineages originated in Asia (specifically China). By contrast, two new H5 viruses identified between 2020 and 2022 that emerged from African and European bird populations indicate a notable shift in H5 epicentre away from Asia and into other continents. These strains were determined to have evolved through genetic reassortment with low pathogenic viral variants as they disseminated. The authors suggest that the increasing persistence of avian influenza in wild bird populations is driving the evolution and spread of new strains.
“These results highlight a shift in the Highly Pathogenic Avian Influenza (HPAI) H5 epicentre beyond Asia and indicate that increasing persistence of HPAI H5 in wild birds is facilitating geographic and host range expansion, accelerating dispersion velocity and increasing reassortment potential,” they write.
The authors suggest that these findings highlight the continued relevance of elimination strategies to limit viral spread and to control the prevalence of highly pathogenic avian influenza within global bird populations, as well as the importance of understanding viral evolution to mitigate and react to new strains.
