( w study conducted by an international ...)Scientists find mutations that let bird flu adapt to humans

The work helps flesh out the changes that have occurred in the worrisome strain of avian influenza virus known as H5N1, a strain some fear could be the organism that will trigger a pandemic of virulent human influenza. The avian virus has already changed dramatically from when it was first identified in 1997, says Kawaoka, who also holds an appointment at the University of Tokyo.

"There are big differences between the virus first found in 1997 and the virus we see now," Kawaoka explains. "We are watching this virus turn itself into a human pathogen."

The mutations found by Kawaoka's group have not yet conferred a complete ability on avian flu to easily recognize the topography of human cells, but they are key steps on that pathway. More mutations, says Kawaoka, will be required for the virus to fully adapt to humans, but it is not known how many mutations are needed for such a change.

However, if scientists are able to continue to monitor and secure viral isolates from humans infected with bird flu, they may be able to map a mutation trajectory that will help predict when the avian virus will cross the threshold to become a human pathogen.

The last two flu pandemics in 1957 and 1968 were caused by avian viruses that had accumulated enough genetic mutations to be considered hybrids of animal and human viruses, Kawaoka notes.
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Source:University of Wisconsin-Madison