Researchers in China have created a batch of designer viruses by selectively combining genes from the H5N1 bird flu virus with those of the H1N1 swine flu strain. This reassortment process — which can happen naturally in nature — resulted in several hybridized strains that were able spread through the air and infect mammals.
There is no evidence that H5N1 and H1N1 have ever mixed-and-matched genes on their own, but Chinese scientists are trying to get a leg up on the possibility. It's a similar strategy to the one employed by U.S. and Dutch researchers who deliberately modified the H5N1 virus into a human-contagious form. The idea is to know the enemy — and develop possible countermeasures — before it strikes. The danger/fear, of course, is that the virus could escape from the lab and wreak havoc in human populations.
It's not known if the new hybridized viruses can infect humans.
Ed Yong reports in Nature News:
[Hualan] Chen’s team mixed and matched seven gene segments from H5N1 and H1N1 in every possible combination, to create 127 reassortant viruses, all with H5N1’s HA gene. Some of these hybrids could spread through the air between guinea pigs in adjacent cages, as long as they carried either or both of two genes from H1N1 called PA and NS. Two further genes from H1N1, NA and M, promoted airborne transmission to a lesser extent, and another, the NP gene, did so in combination with PA...
...It is unclear how the results apply to humans. Guinea pigs have bird-like receptor proteins in their upper airways in addition to mammalian ones, so reassortant viruses might bind in them more easily than they would in humans.
And scientists do not know whether the hybrid viruses are as deadly as the parent H5N1. The hybrids did not kill any of the guinea pigs they spread to, but Chen says that these rodents are not good models for pathogenicity in humans.
There is also a chance that worldwide exposure that already occurred to the pandemic H1N1 strain might actually mitigate the risk of a future pandemic by providing people with some immunity against reassortants with H5N1. In an earlier study, Chen and her colleagues showed that a vaccine made from pandemic H1N1 provided some protection against H5N1 infections in mice