Genetic, biological and epidemiological study on a cluster of H9N2 avian influenza virus infections among chickens, a pet cat, and humans at a backyard farm in Guangxi, China

ABSTRACT

During an investigation in October 2018, two people with diarrhoea, mild abdominal pain, and mild arthralgia symptoms in Guangxi, China, were identified as infected by H9N2 avian influenza virus (AIV). Four H9N2 AIVs were isolated from one of two patients, a pet cat, and a dead chicken (two respective isolates from its lung and kidney tissues) bred by the patients at a backyard farm. Epidemiological investigation indicated that the newly bought chicken died first, and clinical syndromes appeared subsequently in the two owners and one cat. Furthermore, the two individuals possessed high H9N2-specific hemagglutination inhibition and microneutralization antibodies. Shared nucleotide sequence identity (99.9% – 100%) for all genes was detected in the four H9N2 isolates, and hemagglutinin (HA) T138A located on the receptor binding domain (RBD), resulted from nucleotide polymorphisms that were exclusively found in the isolate from the female patient. Moreover, HA K137N on the RBD was found in isolates from these three host species. Importantly, these four H9N2 isolates presented an exclusive binding preference for the human-type receptor (α2-6-SA), and could replicate and cause pathological changes in mice. Phylogenetic analyses showed that these four isolates clustered together and belonged to clade C1.2, lineage Y280. In addition, H9N2 viruses of human origin are genetically divergent and interspersed with the widespread poultry-origin H9N2 AIVs. All these results indicate a high risk of H9N2 AIVs in public health, and effective prevention and control measures against H9N2 AIVs should be considered and performed for both animal and human health.

KEYWORDS:

• H9N2
• avian influenza virus
• interspecies transmission
• genetic evolution
• public health risk

Acknowledgements

We thank the submitters for the genome of influenza viruses in GISAID and NCBI databases. We also would like to thank Alexander J. Millman, Todd Davis, Ying Song, and Ran Zhang for their suggestions for this manuscript.

Disclosure statement

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

Declaration of interest statement

The authors report there are no competing interests to declare.

Additional information

Funding

This work was supported by National Key R&D Program of China: [Grant Number 2021YFC2300900, 2021YFE0109100]; Strategic Priority Research Program of Chinese Academy of Sciences: [Grant Number XDB29010102]; National Natural Science Foundation of China: [Grant Number 3216123001, 31870163]; China-U.S. Collaborative Program on Emerging and Re-emerging Infectious Diseases: [Grant Number 5U01IP001106-01]; Self-supporting Program of Guangzhou Laboratory: [Grant Number SRPG22-001]; Shenzhen Science and Technology Research and Development Project: [Grant Number JCYJ20180504165549581]; National Science and Technology Infrastructure of China: [Grant Number NPRC-32]; Special Program of China Postdoctoral Science Foundation: [Grant Number 2020T130123ZX]; Youth Innovation Promotion Association CAS: [Grant Number Y2021034]; Innovation Team and Talents Cultivation Program of National Administration of Traditional Chinese Medicine: [Grant Number ZYYCXTD-D-202208].