TUESDAY, Oct. 31 (HealthDay News) -- A new strain of avian influenza has been found in market poultry in southern China in the last year, which has already spread throughout Southeast Asia and is responsible for some recent cases of human infection in China, according to a study published Oct. 30 in the Proceedings of the National Academy of Sciences Early Edition. The researchers suggest that this variant may be responsible for a third wave of avian flu.
Robert G. Webster, Ph.D., and colleagues from the University of Hong Kong, surveyed H5N1 influenza strains found in market chickens, ducks and geese in six provinces in southern China from July 2005 to June 2006.
The researchers found that 2.4 percent of poultry were positive for H5N1, with most isolates found in ducks and geese. Genetic and antigenic analyses showed that many of the recent isolates formed a distinct H5N1 sublineage termed Fujian-like.
This strain eventually replaced other regional sublineages by October 2005 and has been transmitted to Hong Kong, Laos, Malaysia and Thailand, according to the study. The Fujian-like sublineage has also been responsible for recent human infection in China. Vaccinated market poultry had low H5N1 seroconversion rates, and the team suggests that vaccination may even have aided the emergence of this new strain.
"The predominance of this virus over a large geographical region within a short period directly challenges current disease control measures," Webster and colleagues conclude. They add that "it is likely that this variant has already initiated a third wave of transmission throughout Southeast Asia and may spread further in Eurasia."
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