A strain of bird flu has moved a step closer to developing the traits required to create an epidemic of the disease in humans, scientists warned on Monday.
Researchers who analysed samples of recent avian flu viruses found that a strain of the virus called H7N2 had adapted slightly better to living in mammals.
Tests on ferrets proved the strain could be passed between animals but scientists said the evidence suggested that bird flu could be transmitted between humans.
Dr Terrence Tumpey, a microbiologist with the US Centers for Disease Control and Prevention, in Atlanta, Georgia, said: "The finding underscores the necessity for continued surveillance and study of these viruses as they continue to resemble viruses with pandemic potential."
The virus tested on the ferrets - a standard animal model of flu in humans - was isolated from a man in New York in 2003, where it thrived on the same sugars found in the human windpipe.
