The H5N1 bird flu virus has mutated to infect people more easily, although it still has not transformed into a pandemic strain, researchers reported.
The changes are worrying, said Yoshihiro Kawaoka of the University of Wisconsin-Madison. "We have identified a specific change that could make bird flu grow in the upper respiratory tract of humans," said Kawaoka, who led the study. The viruses that are circulating in Africa and Europe are the ones closest to becoming a human virus."Recent samples of virus taken from birds in Africa and Europe all carry the mutation, Kawaoka and colleagues report in the Public Library of Science journal PLoS Pathogens."I don't like to scare the public, because they cannot do very much. But at the same time it is important to the scientific community to understand what is happening," Kawaoka said in a telephone interview.