Abstract
In May 2014, China formally confirmed the first human infection with the novel H5N6 avian influenza virus (AIV) in Sichuan Province. Before the first human case was reported, surveillance of AIVs in wild birds resulted in the detection of three H5N6 viruses in faecal samples from migratory waterfowl in Chenhu wetlands, Hubei Province, China. Genetic and phylogenetic analyses revealed that these three novel viruses were closely related to the H5N6 virus that has caused human infections in China since 2014. A Bayesian phylogenetic reconstruction of all eight segments suggests multiple reassortment events in the evolution of these viruses. The hemagglutinin (HA) and neuraminidase (NA) originated from the H5N2 and H6N6 AIVs, respectively, whereas all six internal genes were derived from avian H5N1 viruses. The reassortant may have occurred in eastern China during 2012–2013. A phylogeographic analysis of the HA and NA genes traced the viruses to southern China, from where they spread to other areas via eastern China. A receptor-binding test showed that H5N6 viruses from migratory waterfowl had human-type receptor-binding activity, suggesting a potential for transmission to humans. These data suggest that migratory waterfowl may play a role in the dissemination of novel H5N6 viruses.
Highlights
Wild birds are known to play a major role in the evolution, maintenance, and spread of the avian influenza viruses (AIVs)
H7N9 influenza viruses during early 2013 in China, active surveillance of AIV in wild birds was undertaken in the Chenhu wetlands
The results of this study showed that three H5N6 isolates were recovered from fresh droppings of migratory birds before the first human H5N6 infection case occurred
Summary
Wild birds are known to play a major role in the evolution, maintenance, and spread of the avian influenza viruses (AIVs). Wild birds are thought to play a role in the unexpected appearance of novel influenza A viruses in poultry, swine, equines, and humans[2]. A novel reassortant human-infecting avian influenza A (H7N9) virus, first identified in China in March 2013, contains the neuraminidase (NA) gene from wild ducks in South Korea[10]. After the outbreak of H7N9, fatal human infections with a novel H10N8 virus were reported in China[11], and the H10 gene was shown to have been introduced to domestic ducks by migratory ducks on Poyang Lake in multiple events[12]. We report the isolation and characterization of three previously unrecognized novel avian influenza A (H5N6) viruses in migratory waterfowl before the first human infection was reported
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