Flu mutates quicker than thought 

  Flu viruses can swap many genes rapidly to make new resistant strains,
  US researchers have found. Scientists previously believed that gene
  swapping progressed gradually from season to season.

  The findings in PLOS Biology suggest strains could vary widely each
  season, making it potentially harder to treat. They also increase
  concerns about bird flu mutating to spread readily between humans. 

  Dr David Lipman and colleagues looked at strains of influenza A that
  had circulated between 1999 and 2004 in New York. 

  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. 

  Dr Lipman's team found wide variations in the 156 strains that they
  analysed. Some of the strains had at least four gene swaps that had
  occurred in a short time period. "The genetic diversity of influenza
  A virus is therefore not as restricted as previously suggested," said
  the researchers. 

  Scientists have been particularly worried recently about avian flu
  mutating and acquiring the ability to spread from human to human. 

  If it does, it could kill millions worldwide. 

  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. 

  "The situation could be similar in the bird flus as well." 

http://news.bbc.co.uk/1/hi/health/4717183.stm

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