Insights gained from influenza genomic sequence data: frequent intrasubtype reassortment

Studies using whole genomic influenza sequence data produced by the Influenza Genome Sequencing Project (IGSP) have focused mainly on influenza evolution and epidemiology. For instance, IGSP data has provided important insight into the frequency of intrasubtype reassortment (in which reassortment occurs between different segments of the Influenza genome). The data suggests that reassortment occurs frequently, leading to viruses with altered antigenic properties that may evade current vaccines. Thus, it is useful to study not only the HA and NA segments that produce the hemagglutinin and neuraminidase proteins that sit on the surface of the virion and interact with host cells, but the whole viral genome, as this provides a complete picture of the emergence of the virus (E.C. Holmes, 2009).

The significance of intrasubtype reassortment for strain emergence was shown by the appearance of the new strain of Influenza H1N1 in 2009, which is a reassortant virus containing multiple swine influenza lineages.

In the October 2010 publication by Ilyushina et al, they show that despite the lack of detection thus far in humans, viable seasonal/pandemic Influenza virus reassortants can be generated in a laboratory setting. Their study showed that intrasubtype reassortment is able to occur between seasonal H3N2 and pandemic H1N1 viruses, potentially leading to the emergence of a strain with higher virulence.