Evolution isn't always for our benefit: studies show that the avian flu virus - otherwise known as H5N1, the bird flu - has evolved to be able to infect the cells of the upper respiratory system in mammals. This evolution may become the means for the virus to become a human epidemic.

The virus first occurs among birds, but humans in close contact with infected animals may become infected as well. While human infections are special cases, virologists believe that the virus may soon evolve to allow human-to-human infection and cause a pandemic. The process may take time, maybe years, but it is a possibility.

The evolution that researchers have observed is only a small change, but it is enough to see where the process is ultimately headed for. By evolving to be able to infect the upper respiratory system, the virus can more easily spread among mammals, which of course includes us.

The head of the research team, Yoshihiro Kawaoka, explains:

The viruses that are in circulation now are much more mammalian-like than the ones circulating in 1997. [The change] may provide a platform for the adaptation of avian H5N1 viruses to humans and for efficient person-to-person virus transmission. [...] This change is needed, but not sufficient. There are other viral factors needed to cause a viral pandemic.