Some people may be at risk of a severe reaction to flu because they are not protected by a key gene, scientists suggest.
Researchers have for the first time identified a human gene responsible for susceptibility and response to flu and other viruses.
The gene - IFITM3 - produces a protein that protects cells against infections and is thought to be critical in the immune system’s response against viruses such as swine flu.
Scientists think that when the protein produced by the normal IFITM3 gene is present in large quantities, the spread of flu in the lungs is hindered. When protein levels are lower the virus can spread more easily causing severe symptoms.
The study found that patients who ended up in intensive care with potentially fatal complications after developing flu were much more likely to have a variant of this gene, that did not protect against the virus.
The research was led by the Wellcome Trust Sanger Institute working in collaboration with scientists from The Roslin Institute at the University of Edinburgh and clinicians at NHS Lothian.
They said the findings “strongly suggest” that it plays a key role in flu susceptibility and reduced ability to fight the infection.
The study, called the Genetics of Influenza Susceptibility in Scotland (GenISIS) started when the swine flu pandemic hit Scotland.