Researchers involved in a study at the University of Wisconsin have discovered that the H5N1 Avian Flu virus has mutated into a strain that may make humans more vulnerable to the disease.

Prior to the study, it was known that the virus could only thrive or live in a body which have temperatures of 106°F (41°C). A human's normal body temperature is 98.6°F (37°C). This difference in the temperatures of bodies makes the virus less likely to infect a human, but the recent study suggests the virus has adapted to survive in bodies with temperatures lower than 106°F.

"We have identified a specific change that could make bird flu grow in the upper respiratory tract of humans," said Yoshihiro Kawaoka, the researcher in charge of the study.

Kawaoka also stated that the "viruses that are circulating in Africa and Europe are the ones closest to becoming a human virus," but also stated that the H5N1 virus must undergo several mutations before it can infect a human, who can then spread the virus to other humans.

"Clearly there are more mutations that are needed. We don't know how many mutations are needed for them to become pandemic strains," added Kawaoka.
The World Health Organization (WHO) has stated that despite the study, influenza viruses are constantly mutating from season to season, but that the H5N1 virus is not anymore deadly to humans than before the study.

"Mutations occur in influenza viruses. Separately from that, the (bird flu) virus continues to be deadly. But there is no new jump in deadliness," said Gregory Hartl, a spokesman for the WHO.