Genetic and biological characteristics of the globally circulating H5N8 avian influenza viruses and the protective efficacy offered by the poultry vaccine currently used in China

Abstract

The H5N8 avian influenza viruses have been widely circulating in wild birds and are responsible for the loss of over 33 million domestic poultry in Europe, Russia, Middle East, and Asia since January 2020. To monitor the invasion and spread of the H5N8 virus in China, we performed active surveillance by analyzing 317 wild bird samples and swab samples collected from 41,172 poultry all over the country. We isolated 22 H5N8 viruses from wild birds and 14 H5N8 viruses from waterfowls. Genetic analysis indicated that the 36 viruses formed two different genotypes: one genotype viruses were widely detected from different wild birds and domestic waterfowls; the other genotype was isolated from a whopper swan. We further revealed the origin and spatiotemporal spread of these two distinct H5N8 virus genotypes in 2020 and 2021. Animal studies indicated that the H5N8 isolates are highly pathogenic to chickens, mildly pathogenic in ducks, but have distinct pathotypes in mice. Moreover, we found that vaccinated poultry in China could be completely protected against H5N8 virus challenge. Given that the H5N8 viruses are likely to continue to spread in wild birds, vaccination of poultry is highly recommended in high-risk countries to prevent H5N8 avian influenza.

Emergence, Evolution, and Biological Characteristics of H10N4 and H10N8 Avian Influenza Viruses in Migratory Wild Birds Detected in Eastern China in 2020

“…In the past 2 decades, the avian-origin H5N1, H5N6, H7N9, and H9N2 viruses have acquired the ability to infect mammals without prior adaptation and have led to more than 2,000 human infections in total ( 3 – 8 ). The H5Nx (H5N1, H5N2, H5N3, H5N5, H5N6, H5N8) viruses have evolved to form 10 clades and more than 20 subclades and subbranches and have continually reassorted with other subtypes of AIVs to generate different novel subtypes and genotypes ( 9 – 16 ). The worldwide spread of H5N8 viruses started in 2014, and the viruses have continually circulated in migratory wild birds in Europe, Asia, and Africa in recent years ( 9 , 10 , 17 – 20 ).…”

Emergence, prevalence, and evolution of H5N8 avian influenza viruses in central China, 2020

“…In the Maximum-likelihood (ML) phylogenies of the H5 gene, 2020-H5N8 (n = 40) and SX116-H5N2 were both classified in 2.3.4.4b, and were further diverged into two phylogenetically distinct sub-clades: 2.3.4.4b1 and 2.3.4.4b2 ( Figure 1 ) [ 7 , 32 , 33 ]. The high bootstrap value also supported the two novel sub-clades.…”

The molecular determinants of antigenic drift in a novel avian influenza A (H9N2) variant virus

“…In recent year, novel avian influenza viruses (AIVs) have emerged as a major threat to animal and human [ 1 ]. The focus of global pandemic preparedness is H5 and H7 AIVs [ 2 , 3 ].…”