Two genetically diverse H7N7 avian influenza viruses isolated from migratory birds in central China

Abstract

After the emergence of H7N9 avian influenza viruses (AIV) in early 2013 in China, active surveillance of AIVs in migratory birds was undertaken, and two H7N7 strains were subsequently recovered from the fresh droppings of migratory birds; the strains were from different hosts and sampling sites. Phylogenetic and sequence similarity network analyses indicated that several genes of the two H7N7 viruses were closely related to those in AIVs circulating in domestic poultry, although different gene segments were implicated in the two isolates. This strongly suggested that genes from viruses infecting migratory birds have been introduced into poultry-infecting strains. A Bayesian phylogenetic reconstruction of all eight segments implied that multiple reassortments have occurred in the evolution of these viruses, particularly during late 2011 and early 2014. Antigenic analysis using a hemagglutination inhibition test showed that the two H7N7 viruses were moderately cross-reactive with H7N9-specific anti-serum. The ability of the two H7N7 viruses to remain infectious under various pH and temperature conditions was evaluated, and the viruses persisted the longest at near-neutral pH and in cold temperatures. Animal infection experiments showed that the viruses were avirulent to mice and could not be recovered from any organs. Our results indicate that low pathogenic, divergent H7N7 viruses circulate within the East Asian-Australasian flyway. Virus dispersal between migratory birds and domestic poultry may increase the risk of the emergence of novel unprecedented strains.

Avian Influenza Virus Prevalence and Subtype Diversity in Wild Birds in Shanghai, China, 2016–2018

“…The overall three-year prevalence of influenza A viruses in these wild bird samples was 8.8% as assessed using qRT-PCR (Table 1), and the annual influenza A virus prevalence was 7.5% (122/1622), 9.4% (155/1649), and 9.5% (175/1841) in 2016, 2017, and 2018, respectively. The total prevalence in this study was apparently higher than previous reports in South-eastern China and Central China located on the East Asian-Australasian flyway, which were about 0.65-8% [15][16][17]. The difference in prevalence might be explained by the different sampling species, diagnosis methods, and type of samples.…”

Genetic and antigenic characterization of H5 and H7 avian influenza viruses isolated from migratory waterfowl in Mongolia from 2017 to 2019

“…These factors have contributed to the spread of these viruses to parts of Asia, Europe, Africa, and North America after an outbreak in wild birds at Qinghai Lake in China in 2005 [14]. Circulations of H7 LPAIVs in wild birds and poultry have been reported throughout the world [7,13,[15][16][17][18][19][20]. In addition, H7N9 HPAIVs and LPAIVs are at risk to spread by wild bird and human-caused movements [21,22].…”

Recent progress in chemical approaches for the development of novel neuraminidase inhibitors

“…Various types of inuenza viruses and their infection types are listed in Table 1 for better understanding. [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65]…”