CHINA: Chicken vaccination may have helped a previously unknown and dangerous sub-strain of H5N1 bird flu to emerge in China, new research suggests. The virus, which appeared last year, is now the dominant H5N1 strain in southern China and is spreading through southeast Asia.
In a report published yesterday, scientists said it appeared to have avoided China's compulsory chicken vaccination programme, and may even have been aided by it.
Vaccination could have resulted in survival of the fittest strains, leading to selection of the new variant - described as having a "Fujian-like" (FJ) sub-lineage.
The FJ strain has already transmitted to Hong Kong, Laos, Malaysia and Thailand, resulting in a new epidemic wave.
The strain is thought to be responsible for recent human H5N1 infections in rural and urban areas of China that cannot readily be linked to poultry outbreaks at nearby farms and markets.
Urban infections could challenge current pandemic preparedness plans, the researchers warn in the journal Proceedings of the National Academy of Sciences.
Yi Guan, from the University of Hong Kong, and his colleagues wrote: "The repeated emergence of H5N1 variants from southern China and their subsequent spread to other parts of the world makes it increasingly apparent that implementation of effective control measures in this region is of paramount importance."
The scientists made the discovery by monitoring the H5N1 virus in market chickens, ducks and geese. Since November 2005, a total of 22 cases of human H5N1 infection from 14 Chinese provinces have been reported.
In total, 256 people have been infected and 151 have died since the first outbreaks of H5N1 were reported in 2003. - (PA)