The bird flu virus is mutating and becoming more dangerous to mammals, say researchers. A study, published this week in the Proceedings of the National Academy of Sciences of the USA, shows that over recent years, the virus's ability to kill infected mice has increased.
The investigators took 21 different virus samples isolated since 1997 and used them to inoculate mice. They found that the most recent virus samples killed mice faster than those from earlier years. All of the samples were of a strain of bird flu called HN51, which killed 23 people in Asia earlier this year.
Although humans can contract and die of the disease, they cannot transmit it to other people. But researchers fear that future mutations — or hybridisation with the human flu virus — may enable the virus to spread from person to person.