VIROLOGICA SINICA 2016, 31 (5): 444–447
Influenza A viruses (IAVs) are single-stranded, negative sense RNA viruses. IAV subtype is determined on the basis of the viral surface glycoproteins, hemagglutinin (HA), and neuraminidase (NA). To date, 18 HA and 11 NA subtypes have been reported (Tong et al., 2012). IAVs can cause sporadic infections, local epidemics, and global pandemics among humans. In addition to humans, IAVs can naturally infect avian, swine, equines, canines, and sea mammals (Webster et al., 1992). Migratory waterfowl are the natural reservoir for IAVs, and the avianorigin IAVs play an important role in influenza ecology and have been involved in generation of the IAVs infection in humans. At least one or more genetic segments of all four known pandemic strains are of avian origin, and these avian-origin genes reassorted with those IAVs from domestic animals to generate pandemic viruses. For example, the HA genes (major antigenic determinants) of 1918, 1957, and 1968 pandemic viruses are all of avianorigin (Webster et al., 1997); the 2009 H1N1 pandemic virus has avian-origin PB2 and PA genes (Shinde et al., 2009). Besides pandemic viruses, in the past decades, there have also been a number of reported human infections with avian IAVs, including subtypes H5N1, H6N1, H7N2, H7N3, H7N7, H9N2, H10N7 and H7N9. Thus, monitoring the evolution of avian IAVs and rapidly detecting these viruses in human are important components of influenza surveillance and pandemic preparedness.
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