According to a team from State Key Laboratory of Emerging Infectious Diseases and St. Jude's Children's Research Hospital in Memphis, Tenn., the H5N1 strain still mostly affects birds, and only infects people with close, prolonged association with infected birds or people, but this new strain could be the key to its development into a version easily transmittable between humans. If that happens, it would likely kick off a pandemic that could claim millions of lives.
The team monitored H5N1 in market chickens, ducks and geese, and found the new strain emerged last year, displacing previous strains in southern China by early this year. The compulsory chicken vaccination program did not stop the strain; indeed the scientists suggest it may have even exacerbated the virus.
The new strain has spread across China, especially in urban and rural areas, and also to Hong Kong, Laos, Malaysia and Thailand in what the team is calling a new outbreak wave in Southeast Asia.
"The predominance of this virus over a large geographical region within a short period directly challenges current disease control measures," the team concluded.
"The implications of this study are that current control measures, as generally practiced to control avian influenza, are ineffective," said professor Yi Guan of the University of Hong Kong, leader of the team describing the virus at the proceedings. He added that there was no information yet that suggested the new strain was any more highly pathogenic or a more likely candidate for pandemic than any other H5N1 subtype. A strain currently found in Eurasian and African poultry populations is considered the most likely candidate for pandemic influenza.
However, the new strain illustrates how more frequent and broader flu surveillance is needed in both poultry and humans, the team said, otherwise identifying a human outbreak will be difficult.
According to official World Health Organization figures, H5N1 has so far infected a total of 256 people, 152 of who have died.
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