#18,316
HPAI H5N1 emerged in China nearly 30 years ago, spilling over into humans (n=18) for the first time in Hong Kong in 1997, producing 6 fatalities. This set off alarm bells, and a massive poultry culling campaign, which seemingly eradicated the virus.
But H5N1 would resurface in Hong Kong 5 years later, in two family members with recent travel to Fujian Province (a 3rd family member died, but was not tested).
Within 12 months various lineages of the HPAI H5 virus would turn up in poultry (and occasionally people) in Vietnam, Cambodia, Laos, Thailand, Japan, and Indonesia. The number of human infections - while still small - was increasing, and alarmingly > 70% were fatal.
New clades and genotypes continued to emerge. While most would be evolutionary failures, others increased its fitness.
In 2005 a clade 2.2 H5N1 virus sparked a massive die-off of birds at Qinghai Lake in Tibet (see H5N1 Influenza Continues To Circulate and Change 2006 by Webster et. al.) prior to the virus abruptly spilling over into Russia and then Europe.
The virus would quickly move into the Middle East, and Sub-Saharan Africa, and even make a brief incursion into North America in 2014-2015.
Since then HPAI H5 has evolved into dozens of clades, subclades, and genotypes. Over the past decade we've seen the dominant subtype shift from H5N1 to H5N8, then briefly to H5N6, and finally back to H5N1 in 2020.
More than once during the last decade it seemed as if HPAI H5 was losing momentum, but since 2020 we've seen it greatly increase its ability to infect mammals, as well as many previously unaffected avian species.
Simply put, the clade 2.3.4.4b virus circulating today appears to be a much bigger threat than the H5 viruses of even a few years ago. While no one can predict with any certainty what happens next, a lot of very smart people are understandably concerned.
All of which brings us to an early, unedited version, of a new review by Tom Peacock et al., published yesterday in the journal Nature - on the concerning changes seen in HPAI H5 in recent years.
Since this is not listed as open access, I've only posted the link where you can read it in its entirety.
Highly recommended.
Review
Published: 24 September 2024
The global H5N1 influenza panzootic in mammals
Nature (2024)Cite this article
(Peacock, T., Moncla, L., Dudas, G. et al. The global H5N1 influenza panzootic in mammals. Nature (2024). https://doi.org/10.1038/s41586-024-08054-z - )
