With so much attention currently focused on HPAI H5N1 clade 2.3.4.4b, it is easy to forget that it is just one of an array of zoonotic avian influenza viruses that we are keeping a close eye on.
China continues to report sporadic (and often fatal) H5N6 infections , although it is likely that many cases go unreported.
Similarly, over the past 10 months Cambodia has reported 4 human infections with a different H5N1 strain (CDC Statement On 2 Fatal H5N1 (clade 2.3.2.1c) Cases In Cambodia),
There are others, of course.
We've seen H6N1 infect dogs and jump to at least one human in Taiwan (see Study: Adaptation Of H6N1 From Avian To Human Receptor-Binding), isolated cases of H7N4 in China, and scores of (mostly mild) H9N2 infections (see FluTrackers list) primarily in Asia.
CHINA NHC Reports 1st Human H10N3 Avian Flu Infection - Jiangsu Province
HK CHP: A Cryptic Report of A 2nd H10N3 Case On the Mainland
Cell Host & MIcrobe: Avian H10N7 Adaptation In Harbor Seals
Jiangxi Province Reports 3rd H10N8 Case
A recent study, published in the Journal of Integrative Agriculture, describes these changes and the growing public health threat from H10Nx viruses. Due to its length I've only included the abstract and some excerpts from the discussion.Over time, H10 viruses in China have acquired worrisome mammalian adaptations - and as we've seen with previously H5N1 and H7N9 - internal genes donated from H9N2 viruses (see PNAS: Evolution Of H9N2 And It’s Effect On The Genesis Of H7N9).
Genetic and Biological Properties of H10Nx influenza viruses in China
XU Yi-na *, LI Hai-ling *, LENG Hao-yu, SU Chao-fan, TANG Si-qi, WANG Yong-tao, ZHANG Shi-wei, FENG Ya-li, WU Ya-nan, WANG Da-xin, ZHANG YingShow more
https://doi.org/10.1016/j.jia.2023.10.028 Get rights and content
Under a Creative Commons license
Abstract
H10 subtype avian influenza viruses (AIV) have been circulating in China for forty years. H10 AIVs in China have expanded their host range from wild birds to domestic poultry and mammals, even human. Most of the H10 subtype AIVs reported in China were isolate from the southeast part. Liaoning is in the northeast of China. We isolated an H10N3 AIV, A/chicken/Liaoning/SY1080/2021(SY1080), from live poultry market (LPM) in Liaoning of the northeast of China.SY1080 replicated efficiently in mice lungs and nasal turbinates without prior adaptation. We systematically compared SY1080 with other H10 subtype isolates in China. Phylogenetic analysis showed that SY1080 and most of the H10 strains belonged to the Eurasian lineage. H10 AIVs in China have formed 63 genotypes. SY1080 as well as the H10N3 strains from human infections belonged to G60 genotype.
H10Nx AIV acquired multiple mammalian adaptive and virulence related mutations during circulation and the recent reassortants derived internal genes from chicken H9N2 AIVs.The H10Nx subtypes AIVs posed potential threat to public health. These results suggested we should strengthen the surveillance and evaluation of H10 subtype strains.
(SNIP)
Discussion
We evaluated the genetic and biologic characteristics of the first H10N3 isolate in Liaoning. Meanwhile, we analyzed the evolution and recombination characteristics of all H10Nx strains isolated in China from 1983 to 2021. We found that H10Nx viruses had formed 63 genotypes in China. The main host of H10 AIV had transitioned from waterfowl to chicken. The epidemic area of H10 subtype AIVs in China overlapped with East Asian-Australasian and Central Asian migration routes. The pathogenicity of H10 AIVs increased progressively. Most mammalian-adaptation and virulence associated mutations were found in chicken-origin isolates
(SNIP)
Some of the G60 virus had acquired pandemic causing factors: the human receptor binding ability, mammalian efficient replication ability and mammalian transmission ability (Guo et al. 2022; Li and Chen 2014; Wang et al. 2021; Yin et al. 2021). Therefore, we should pay more attention to viruses in this genotype.
In summary, the H10 subtype viruses, especially the G60 viruses in China had become more adaptive and pathogenic to mammalian host. The H10 viruses had invaded from wild birds to domestic poultry and spread from southeast to northeast of China. There is high possibility for them to cause more human infections. However, there is no human vaccine for H10Nx viruses. Liaoning is also on the Eastern Asian-Australian Flyway of migratory birds and with large poultry industry. But few research on H10Nx was reported before. Our study indicated that Liaoning also faced threat of H10Nx viruses. Therefore, we strongly recommend to enhance the surveillance of H10 subtype viruses
As we've discussed previously (see Viral Reassortants: Rocking The Cradle Of Influenza), Southeast Asia has long been considered `the cradle of influenza’; an area of the world where both human and animal influenza viruses circulate more-or-less year round, and where there are ample opportunities for viruses to spillover (both to, and from, animals).
While the 2009 H1N1 and the 1918 H1N1 pandemic appear to have emerged from the western hemisphere, China has been the springboard for H2N2 (in 1957), H3N2 ( in 1968), and more recently H5N1, H5N6, H5N8, H7N9, H10N3, H3N6 and H3N8 (to name a few).
Surveillance and reporting from Mainland China (and other parts of Southeast Asia) are often lacking - and information is frequently held close to the vest for political and economic reasons - meaning we could be easily be blindsided by the next pandemic threat.
We either use this time wisely, or we risk finding ourselves - once again - ill prepared to deal with whatever comes next.
