Summary
- Qinghai Lake in China has historically been a breeding and stopover site for migratory birds, where historic outbreaks of highly pathogenic avian influenza viruses have occurred during the breeding season.
- Surveillance in 2022–23 detected the reappearance of highly pathogenic H5N1 strains at Qinghai Lake (genotype G1) that were more virulent when mice were infected than equivalent viruses isolated from same host species one year earlier.
- Analyses showed a genetic relationship among Qinghai Lake H5N1 viruses and strains from East Asian as well as Central Asian regions.
- The mutations of the 2022 viral strains had been linked with enhanced virulence and replication in mammals, thereby implicating a risk for potentially jumping into livestock grazing around Qinghai lake.
- It is imperative to maintain the surveillance of avian influenza viruses among wild birds at Qinghai Lake in order to prevent future outbreaks and monitor potential spillovers into human population or animal species.
Heath officials have identified a new breed of avian influenza referred to as H5N1 clade 2.3.4.4b in the Qinghai Lake region, China. The “highly pathogenic” H5N1 strain has caused numerous outbreaks over the years. In June 2022, after sampling fecal samples in the wetlands of Qinghai lake during bird breeding season, the new strain has been detected.
Researchers from the Wuhan Institute of Virology and other institutions collected fresh fecal samples containing the H5N1 virus as well as decomposed bird corpses in that area. Laboratory testing confirmed the presence of the virus. Following this, an H5N1 outbreak eventually caused a large bird die-off when surveillances resumed in July 2022.
Subsequent insight using state-of-the-art sequencing approaches revealed that the H5N1 viruses circulating in Qinghai Lake fall into clade 2.3.4.4b and genetically cluster with strains detected in other countries situated along bird migratory flyways. These results indicate a close phylogenetic relationship between the Qinghai Lake H5N1 viruses and those from adjacent areas.
The research paper also suggested the possibility of reassortment for genetic between H5N1 virus and other strains co-circulating in this area. This genetic blending could pave the way for new versions of the virus, with functionality and features unlike those seen in their parent strains. Some strains were found to have enhanced virulence and replication abilities, the researchers said, adding that two genotypes of these H5N1 strains had been identified.
Animal studies carried out as part of this study led to the pathogenicity of Qinghai Lake H5N1 strains in mice. The experiments showed that genotypes of the virus differed in their ability to cause disease and some were lethal to test subjects. Importantly, the capacity to infect and replicate efficiently in mammalian hosts raised concerns about cross-species transmission.
Although the H5N1 virus was detected in 2022, surveillance data from 2023 demonstrated that the pandemic strain did not circulate among wild birds. But the scientists warned that as long as it remains in circulation elsewhere, the virus could be reintroduced to Qinghai Lake and cause new outbreaks.
The findings highlight the need for ongoing monitoring of avian influenza viruses in wild birds at Qinghai Lake to detect any possible resurgence of H5N1. The researchers also emphasized that livestock should be monitored for the spread of disease, because it is possible that infected birds could transmit certain diseases to animals and infect cattle on pasture close to the lake.
In conclusion, with the discovery of H5N1 clade 2.3.4.4b virus in Qinghai Lake, the possibility that highly pathogenic avian influenza remains a significant threat. The results of this study will provide useful information about the genetic characteristics and pathogenicity of the virus, which would allow us to be more prepared for future outbreaks.
Infectious Diseases, Public Health & Prevention