- Flu viruses can swap many genes rapidly to make new resistant
strains, US researchers have found.
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- Scientists previously believed that gene swapping progressed
gradually from season to season.
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- The National Institutes of Health team found instead,
influenza A exchanged several genes at once, causing sudden and major changes
to the virus.
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- The findings in PLOS Biology suggest strains could vary
widely each season, making it potentially harder to treat.
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- Sudden mutations
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- They also increase concerns about bird flu mutating to
spread readily between humans.
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- Each year, experts must predict which strains will be
most common and design new vaccines to fight them.
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- Dr David Lipman and colleagues looked at strains of influenza
A that had circulated between 1999 and 2004 in New York.
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- These strains had given rise to the so-called Fujian
strain H3N2 that caused a troublesome outbreak in the 2003-2004 flu season
because the vaccine made that winter was a poor match for the virus.
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- Dr Lipman's team found wide variations in the 156 strains
that they analysed.
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- Some of the strains had at least four gene swaps that
had occurred in a short time period.
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- "The genetic diversity of influenza A virus is therefore
not as restricted as previously suggested," said the researchers.
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- This suggests that scientists need to study circulating
flu viruses more carefully because important mutations can occur suddenly
and without warning, they said.
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- Threat of an outbreak
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- Scientists have been particularly worried recently about
avian flu mutating and acquiring the ability to spread from human to human.
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- If it does, it could kill millions worldwide.
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- Last week, the UK government announced it would stockpile
two million doses of vaccine to combat the H5N1 strain of bird flu currently
circulating in Asia to protect key medical and emergency workers across
Britain against a possible global pandemic.
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- Dr Maria Zambon, flu expert at the Health Protection
Agency said: "This research confirms the genetic diversity of influenza
viruses and underscores potential for reassortment."
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- Professor John Oxford, a virologist at Queen Mary's School
of Medicine, said: "Their work shows that, overall, the virus is a
lot more busy swapping genes than we ever thought it was.
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- "The situation could be similar in the bird flus
as well."
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- Dr John Moore-Gillon, spokesman for the British Lung
Foundation, said: "We need to find a way to attack the flu virus so
it will takcle a wider range of virus.
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- "Currently, flu vaccination is very narrow. We have
to predict what the strains are going to be, then make the vaccine.
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- "This work shows that the virus is wider than we
thought."
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- © BBC MMV
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- http://news.bbc.co.uk/2/hi/health/4717183.stm
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