A new study eases fears that the pandemic H1N1 influenza virus will recombine with seasonal flu to mutate into a more lethal form. The study, reported in the online journal PLoS Currents, shows that the pandemic virus, commonly known as swine flu, grows much faster than seasonal flu viruses and is thus less likely to exchange genetic material with them.
Virologist Daniel Perez of the University of Maryland and his colleagues grew the virus in ferrets, which are considered the best animal model for influenza because their respiratory system is very similar to that of humans. They co-infected the animals with the pandemic H1N1 virus and one of two seasonal flu viruses circulating now (a different H1N1 virus or an H3N2 virus). The animals were sickened by both the viruses, but only the swine flu virus went on to infect other ferrets.
"The H1N1 pandemic virus has a clear biological advantage over the two main seasonal flu strains," Perez said. "I'm not surprised to find that the pandemic virus is more infectious, simply because it is new, so hosts haven't had a chance to build immunity yet."