THE world has yet to see a form of the deadly bird flu virus that could spread easily between people and cause a global outbreak — but that doesn't mean it won't happen, scientists say.
Currently, bird flu, or H5N1 avian flu, can be transmitted from birds to birds, and birds to humans, but not from humans to humans. When it does pass from birds to humans, it is usually fatal.
After studying 15 years of data on bird flu viruses in the wild, researchers said some strains were already part way along the road to acquiring just thee more mutations needed to change into a form that could cause a devastating human pandemic. "The remaining... mutations could evolve in a single human host, making a virus evolving in nature a potentially serious threat," Derek Smith of Britain's University of Cambridge, who led the research, told reporters.
Two earlier studies by researchers in the US and Europe have found that with as few as five mutations, H5N1 flu can become transmissible in the air between mammals, including potentially from person to person.
Their work was highly controversial because they manipulated viruses in the lab to produce the new mutated strains.
Until now, scientists were not sure whether it was possible these same mutations could evolve in nature. But Smith's co-researcher Colin Russell said their study, published on Thursday in the journal Science, showed it was.
"Viruses that have two of these mutations are already common in birds, meaning that there are viruses that might have to acquire only three additional mutations in a human to become airborne transmissible," he told reporters.
So far, the H5N1 virus, which was first detected in Hong Kong in 1997, has infected tens of millions of ducks, geese, chickens and other birds. People who have been infected — so far there have been 606, of whom 357 have died — are mostly those who came into close contact with birds.