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Tuesday, 27 August, 2002, 14:44 GMT 15:44 UK
Gene helps flu beat body's defences
Man sneezes
Sniffles: But killer flu could be just a strain away
Just one gene could help turn a normal flu virus into one capable of causing a deadly pandemic, claim researchers.

While flu viruses are broadly the same, there are hundreds of different strains, and a handful spread rapidly and can prove lethal in even healthy adults.


Sooner or later we're going to get a bad one, and by understanding the beast we've got a better chance of killing it

Dr Robert Webster, St Jude Children's Research Hospital, Memphis
The best example was the Spanish flu of 1918 which killed millions.

However, scientists say they may have discovered a single gene in a flu virus which gives it the potential to cause havoc.

The Hong Kong flu, a strain called H5N1, which jumped from chickens to humans in 1997, appeared able to evade normal body defences.

Immune defence

Normally the body's immune cells start producing large numbers of cytokines, which help trigger a massive immune response in uninfected cells.

This shortens and lessens the extent of the infection.

However, Hong Kong flu did not provoke this cytokine response.

Six people died after the 1997 outbreak, and three million chickens were slaughtered to try to halt the virus.

Nature.com reports that experts at St Jude Children's Research Hospital in Memphis, Tennessee, have identified a particular genetic mutation in the Hong Kong virus.

Knockout gene

When they put this gene into a normally virulent strain of flu, infected pigs became much sicker than those infected with the unmodified virus.

They also stayed infectious for longer periods.

Scientists believe that the 1918 strain might have be similar to Hong Kong flu, and perhaps have been harnessing a gene similar to that in H5N1 to evade the immune system.

Every year, strains of flu that emerge are slightly different from the year before, hence the need for a fresh flu vaccine every season.

There are fears that this constant process of genetic shifting will eventually produce a "super-flu" virus, perhaps incorporating the H5N1 genetic mutation, and cause a major pandemic.

St Jude virologist Dr Robert Webster told Nature.com: "We have to have this information.

"Sooner or later we're going to get a bad one, and by understanding the beast we've got a better chance of killing it."

See also:

31 Jul 02 | Africa
23 May 02 | Health
06 Apr 02 | Asia-Pacific
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