16 March 2012
A distinct lineage of influenza A virus in bats
On January 17 2012, the Proceedings of the National Academy of Sciences published a paper by Tong et al. which described the identification of a new influenza A virus haemagglutinin (HA) type (H17) in yellow-shouldered bats captured in two locations in Guatemala. In addition, all seven other genes were genetically distant from known influenza A viruses. Three of the 316 bats captured over a two year period were positive for the virus, identified through the use of consensus-degenerate RT-PCR/PCR primers. The HA of the bat virus was estimated to have diverged at roughly the same time as the other 16 known subtypes of HA. The bat virus had 45% amino acid sequence similarity to HAs from all 16 other Influenza A subtypes, similar to the relationship held among each of these subtypes. Gene analysis showed that the bat virus was significantly divergent from known influenza A, B and C viruses, however, it was more closely related to group 1 HAs and so was designated as H17, although definitive taxonomic classification is still needed. The neuraminidase (NA) gene was also highly divergent from all known influenza NAs suggesting an older ancestral relationship to known influenza viruses. Unsuccessful attempts were made to propagate the virus in chicken embryos and cell cultures; however, parts of the bat virus genome appeared to be compatible with regions of the human influenza virus genome, suggesting that reassortants of bat and human viruses may not be incompatible. The authors concluded that this identification expands the repertoire of likely reservoirs of influenza viruses and suggested that further research into how the virus is maintained within bat populations and whether there are other potential influenza reservoirs be investigated.
Influenza viruses have been previously reported to infect bats and the public health significance of this new virus is unknown. The emergence of global influenza pandemics in human populations can often be traced back to mammalian reservoirs, as was seen in the 1918 and 2009 influenza A H1N1 swine-origin outbreaks. In both cases the virus had been circulating in pig populations for a notable length of time undergoing significant reassortment before outbreaks were seen in humans. An understanding of the evolutionary genomics of this H17 virus over time can help in reducing any potential future risk of an outbreak in human populations. The recent appearance of other viruses from bat reservoirs including Hendra and Nipah viruses raises the concern that further encroachment on bat habitats may increase the chance of transmission of novel viruses to humans either directly or through other mammalian species.
1.Tong, S., Lia, Y., Rivailler, P., Conrardy, C., Castillo, D.A.A., Chen, L., Recuenco, S., Ellison, J.A., Davis, C.T., York, I.A., Turmelle, A.S., Moran, D., Rogers, S., Shi, M., Tao, Y., Weil, M.R., Tang, K., Rowe, L.A., Sammons, S., Xu, X., Frace, M., Lindblade, K.A., Cox, N.J., Anderson, L.J., Rupprecht, C.E., Donis, R.O. A distinct lineage of influenza A virus from bats. Proceedings of the National Academy of Sciences, 2012.
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