Hong Kong - A vaccine used to stop outbreaks of the deadly
bird flu virus in chickens in Hong Kong for the last seven years is
losing its effectiveness, a leading microbiologist warned Tuesday.
Professor Yuen Kwok-yung said the vaccine, which protects chicken
from the H5 strain of the virus, is becoming less effective and the
city risks further outbreaks because total failure is inevitable.
The head of microbiology at the University of Hong Kong told the
South China Morning Post the virus was mutating and shifting away
from the Fujian strain of H5N2 that it was developed for.
His warning follows an outbreak of H5N1 virus in four wet markets
in Hong Kong in June, the first in years in the former British
colony.
Yuen, who is part of a team investigating the outbreak, said the
city must get rid of all live chickens in markets before the vaccine
becomes completely ineffective.
He said tests showed that in 2005 vaccine was producing only a
quarter of the antibodies to protect against the virus compared to
the level produced by the same vaccine in 2001.
He said some chickens showed an antibodies level at the 'alarm
stage' which meant the protection was minimal.
'It is only a matter of time before it will lose its protection,'
said Yuen, who is urging the government to ban all live chicken
markets in Hong Kong before the vaccine, developed in the
Netherlands, becomes ineffective.
'It takes time for the manufacturers to produce new vaccines,' he
said. 'Hong Kong is taking its own risk if it still has live chickens
in the markets.'
The government has yet to identify the source of the latest
outbreak which resulted in the culling of thousands of chickens and
led to tighter restrictions on imports and a ban on overnight
stocking of live chickens in markets.
Live chicken sales resumed July 2 after a 21-day ban on import and
sales following the outbreak.
Hong Kong was the scene of the first outbreak of bird flu to jump
the species barrier in modern times when six people died and 12
others were infected in 1997.
Tough new hygiene and monitoring controls were introduced and Hong
Kong has been spared further human infections from the recent bird
flu cases across the Asia region.
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