New Strain Of Bird Flu Spreads To Humans
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New strain of bird flu spreads to humans
By Roger Highfield, Science Editor
Last Updated: 1:27am GMT 31/10/2006
A previously unknown and dangerous strain of the H5N1 bird flu has emerged from southern China and has spread from birds to people in South-east Asia, marking a third wave of avian flu and rekindling fears of a global pandemic.
Although the H5N1 avian influenza mostly affects birds and infects people only sporadically, the new strain will once again raise fears that it may mutate or combine with a human virus to form a mutant or hybrid capable of passing from person to person, triggering a pandemic where millions of lives may be lost.
"The implications of this study are that current control measures, as generally practised to control avian influenza, are ineffective," said Prof Yi Guan of the University of Hong Kong, leader of a large team that describes the virus today in the Proceedings of the National Academy of Sciences.
Prof Guan, director of the State Key Laboratory of Emerging Infectious Diseases, who collaborated with Prof Robert Webster of St Jude's Children's Research Hospital in Memphis, a leading centre in the West, concludes that "the pandemic threat persists".
"We have no information to suggest that this is more highly pathogenic or that this virus is a more likely candidate for a pandemic virus than any other H5N1 or other subtype virus," he told The Daily Telegraph. However, the team points out that a highly pathogenic H5N1 influenza virus in Eurasian and African poultry populations is considered the most likely candidate for a new pandemic influenza and the rise of avian-to-human interspecies transmission seen in the last 12 months "seems to favour such a hypothesis".
For today's study, the team searched for different viral strains by monitoring the H5N1 avian influenza virus in market chickens, ducks, and geese. The researchers found that a strain emerged last year and became the dominant strain in southern China by early this year, displacing previous ones. The strain appeared to avoid China's compulsory chicken vaccination programme, and may even be aided by the vaccine, which may be ineffective against the new strain.
The new strain was also responsible for recent human H5N1 infections in China, which have occurred in rural and urban areas, some of which could not be linked to nearby outbreaks in farms or local markets. The researchers warn that such urban human infections could lead to a serious outbreak, challenging current pandemic preparedness plans.
These new viruses have already transmitted to Hong Kong, Laos, Malaysia and Thailand, resulting in a new transmission and outbreak wave in South-east Asia, say the team. "The predominance of this virus over a large geographical region within a short period directly challenges current disease control measures," the team concludes.
This strain may have begun the third wave of transmission of H5N1 avian flu that could potentially spread throughout Eurasia. Without more and broader flu surveillance in both poultry and humans, say the researchers, identifying an outbreak of human H5N1 influenza will be difficult.
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