Global dissemination of H5N1 influenza viruses bearing the clade 2.3.4.4b HA gene and biologic analysis of the ones detected in China

ABSTRACT

H5N1 avian influenza viruses bearing the clade 2.3.4.4b hemagglutinin gene have been widely circulating in wild birds and are responsible for the loss of over 70 million domestic poultry in Europe, Africa, Asia, and North America since October 2020. During our routine surveillance, 13 H5N1 viruses were isolated from 26,767 wild bird and poultry samples that were collected between September 2021 and March 2022 in China. To investigate the origin of these Chinese isolates and understand their genetic relationship with the globally circulating H5N1 viruses, we performed a detailed phylogenic analysis of 233 representative H5N1 strains that were isolated from 28 countries. We found that, after they emerged in the Netherlands, the H5N1 viruses encountered complicated gene exchange with different viruses circulating in wild birds and formed 16 genotypes. Genotype one (G1) was predominant, being detected in 22 countries, whereas all other genotypes were only detected in one or two continents. H5N1 viruses of four genotypes (G1, G7, G9, and G10) were detected in China; three of these genotypes have been previously reported in other countries. The H5N1 viruses detected in China replicated in mice, with pathogenicity varying among strains; the G1 virus was highly lethal in mice. Moreover, we found that these viruses were antigenically similar to and well matched with the H5-Re14 vaccine strain currently used in China. Our study reveals the overall picture of H5N1 virus evolution and provides insights for the control of these viruses.

KEYWORDS:

• Avian influenza virus
• H5N1
• clade2.3.4.4b
• evolution
• pathogenicity
• antigenicity

Acknowledgments

We thank the authors and laboratories who submitted sequences to the GISAID EpiFlu Database.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

P.C., J.S., C.W., Y.Z., X.X., H.K., C.Y., X.Z., L.L., G.T., C.L., and G.D. conducted the experiments; P.C., J.S., and H.C. analyzed the data; H.C. wrote the manuscript.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China: [Grant Number 2021YFD1800200, 2021YFC2301700]; the National Natural Science Foundation of China: [Grant Number 31521005, 32192451, 31802191, 31672593]; the Laboratory for Lingnan Modern Agriculture Project: [Grant Number NT2021007]; and by the China Agriculture Research System: [Grant Number CARS-41G12].