Scientists in the Netherlands have warned that the H5N1 bird flu virus could change to a form which would make it possible to spread between humans and lead to a pandemic.
In a study published in the journal Science, researchers identified a small number of mutations which were necessary to change the virus so that it can spread rapidly through the respiratory system.
The study was delayed for several months as various agencies around the world feared the information could be used by terrorists to create a bioweapon.
Writers of the publication, however, believe the research can now be used to speed the development of vaccines and anti-viral drugs against a lethal form of bird flu.
They added that researchers have proven that it is safe to publish the study and that the research was conducted under safe conditions.
Erasmus Medical Centre, which led the study, showed that five to ten mutations are necessary before the virus becomes transmissible by air.
Initially, the researchers determined how viruses that had caused a pandemic in the past had developed.
Ron Fouchier, Erasmus MC professor, said: "What genetic changes were apparent in these viruses from 1918, 1957 and 1968? Using this knowledge we manipulated the avian influenza virus in such a way that it became transmissible by air.
"They succeeded in doing this after repeatedly passing the virus in the ferret’s nose. Eventually the ferrets started sneezing and coughing thereby infecting other ferrets."
The H5N1 virus has been responsible for the deaths of tens of millions of birds and has led to hundreds of millions more being slaughtered to stop its spread.
The virus is also deadly to humans but can only be transmitted by close contact with infected birds.
Image: Research suggests that five to ten mutations are necessary before the H5N1 virus becomes transmissible by air. Photo courtesy of: FreeDigitalPhotos.net.