A senior scientist at the World Health Organisation (WHO) said today that a limited number of migratory birds appear to be spreading a single sub-strain of the H5N1 virus, a potentially positive discovery.
In theory, this could lower opportunities for the lethal H5N1 virus to mutate into an easily transmissible form which could spark a human influenza pandemic, according to Michael Perdue, an epidemiologist in WHO's global influenza programme.
Scientists are increasingly convinced that some migratory waterfowl carry the lethal virus in its highly pathogenic form, introducing it to poultry flocks along their routes.
Four family groups of the H5N1 virus have been identified, with multiple substrains within each, but it appeared that only one was "moving westward," Perdue said.
"We are looking at what I think is probably limited (migratory bird) species that are infected with what appears to be a single sub-strain of the Asian viruses," he told reporters.
"That is better news than thinking all the birds are spreading the virus all over the world - that's not happening. In that sense, it's not as grim perhaps as it looks," he said.
Perdue later told reporters: "It could reduce the mutation level...You are less likely to have widespread mutation than if you had 20 strains hop-skotching across Asia."
"It also appears that this virus is relatively stable."
The WHO has said that the viruses from Turkey's first two fatal human cases were virtually identical to viruses from Qinghai Lake nature reserve in central China, where there was an unprecedented die-off of 6,000 migratory birds in April 2005.