Influenza viruses are a great threat to humans and have very well proven their pandemic nature such as the H1N1 pandemic in 2009. They contain the protein haemagglutinin (HA) which determines the host range by identifying specific receptors such as sialic acid linked to galactose by α2,6-linkages in humans. Recent studies at UW-Madison and University of Tokyo by Yoshihiro Kawaoka have identified a reassortant H5 HA/H1N1 virus that can be transferred through droplet transmission in a ferret model and is capable of identifying Siaα2,6Gal linkages.

Humans are not immune to viruses containing H5 HA, and thus a virus with transmissible H5 HA would cause a pandemic. Hence, an H5N1 with the ability to transmit among mammals would be very dangerous. H5N1 lack the ability to identify the receptors in humans. To identify H5 HA that can allow human type receptor binding, random mutations were introduced in the HA of H5N1; VN1203. H5N1 library was made with the mutated HA gene and the remaining six viral genes from H1N1; PR8. From the 370 viruses they generated, 8 agglutinated Siaα2,6Gal in Turkey RBCs. Further tests revealed four mutations in the H5 HA that can render droplet transmission ability to the virus and make the HA highly stable. These mutations are changes in the amino acid sequence in the HA.

The two viruses, i.e, H5N1 and the H1N1, have been found in pigs, which are considered as “mixing vessels” for the viruses. As the H5N1 virus continues to evolve, it can very likely lead to a mutation that renders HA droplet transmissible, giving it a pandemic nature along with the genes from H1N1. Hence, although the H5N1 are of no pandemic danger yet, it is very likely that they can acquire droplet transmissible ability in the near future. This new finding calls for proper research in generating vaccines against H5N1 with such ability as in the reassortant.