Scientists reveal the evolutionary picture of the new H5N1 avian influenza virus

Origin, evolution and spatiotemporal transmission of H5N1 subtype avian influenza virus. Courtesy of the Chinese Academy of Agricultural Sciences

Recently, the team of academician Chen Hualan of the Harbin Veterinary Research Institute of the Chinese Academy of Agricultural Sciences has made important progress in the research of H5N1 subtype of highly pathogenic avian influenza virus, which elucidates the origin, evolution and spatio-temporal transmission of the H5N1 avian influenza virus that is currently raging around the world, and conducts systematic biological research on the H5N1 virus detected in China. The findings were published in Emerging microbes & infections.

The study found that the currently circulating H5N1 virus, which was produced in the Netherlands in October 2020, was recombined by the H5N8 avian influenza virus with subtypes of avian influenza viruses such as H1N1 and H3N8.

From October 2020 to August 2021, the new H5N1 virus was endemic in poultry and wild birds in many countries in Western, Northern and Eastern Europe, and spread to several African countries. Beginning in September 2021, it caused a major outbreak of bird flu in Europe and spread to several countries in Asia and North America. Since January 2020, the H5N8 and H5N1 viruses have killed or culled more than 200 million poultry worldwide. Due to the widespread use of avian influenza vaccine immunization, these new H5 viruses have not caused substantial harm to poultry in our country.

The National Avian Influenza Reference Laboratory collected 26,767 wild bird and poultry samples nationwide between September 2021 and March 2022, from which 13 strains of H5N1 virus were isolated.

In order to explore the origin of these newly introduced H5N1 viruses in China, the researchers conducted systematic genetic evolution and spatiotemporal transmission analysis of 233 H5N1 subtype representative strains in the world. It was found that since the current globally circulating H5N1 virus first appeared in the Netherlands in October 2020, it has undergone complex genetic fragment reprogramming with a variety of wild bird-derived avian influenza viruses in nature, forming 16 different genotypes (G1-G16).

Four genotypes were detected in China, namely G1, G7, G9 and G10. Among them, G1 and G10 were introduced to China by Europe in November 2021 and January 2022 respectively, and G7 was introduced to China by South Korea or Japan in November 2021, and the source of G9 is unclear.

Antigenicity analysis showed that the H5-Re14 vaccine strain currently used in China matched its antigenicity well, which proved that the inactivated vaccines of H5 and H7 trivalent avian influenza can effectively block the invasion of such H5N1 viruses into immune poultry. Given the widespread distribution of such H5N1 viruses in wild birds around the world, the article calls on high-risk countries to immunize poultry against H5 subtype avian influenza vaccine, effectively blocking the spread of the virus from wild birds into poultry, thereby effectively reducing the threat to human health.

The research has been funded by the National Natural Science Foundation of China, the National Key Research and Development Program, and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences. (Source: China Science Daily Li Chen)

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