Air pollution also plays a role in severity: allergic reactions are caused by the body overreacting to proteins found in allergens.

London - Tried everything and still got the flu this year? And have you noticed how some friends and colleagues always seem to avoid it?

Well, they may have more than luck on their side. Scientists have discovered that, however, hard you try to avoid it, flu is in your genes.

A study on British volunteers shows that some people are genetically predisposed to stave off the illness, while others are struck down year after year. The good news for the unlucky ones is that the discovery could form the basis of a universal treatment.

Researchers inoculated 17 healthy people with the flu virus and monitored their progress for five days. Of the sample, nine became ill and the rest showed no symptoms at all.

Using technology usually employed in satellite imaging, they examined the genes in the subjects’ blood samples every eight hours. Those who became sick developed an acute inflammation on certain genes 36 hours before the symptoms set in. This “genetic signature” was most marked in those who were suffering the worst.

Those who remained fine were found to have activated a different genetic signature.

The scientists interpreted this signature as an “anti-stress response” that showed their bodies were actively fighting off the virus. This discovery raises the possibility that experts could find a way to detect flu early and take preventative action before the worst effects develop.

Professor Peter Openshaw, of the Centre for Respiratory Infection at Imperial College, said: “This is very important science, really Star Trek stuff. It has very big implications for many infectious diseases, not only flu.

Dr Alfred Hero, the University of Michigan academic who led the research, said: “We looked at more than 22 000 genes in 267 blood samples. No study of this magnitude has ever been done on human immune response. We can start to tease out the biological conditions that might make one more resistant to getting sick.

“We will be testing it on different strains of flu, and it may not just be flu, it may be the same for other viruses including the common cold.”

A think-tank recently called for the flu jab to be given to everyone over 50. The International Longevity Centre said that while Britain’s childhood immunisation programme was among the best in the world, adult immunisation had been neglected. – Daily Mail