Study: Why Flu Hits Some People Harder than Others

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During the 2009-10 H1N1 or “swine flu” pandemic, the same virus that caused mild coughing and sneezing in some patients proved fatal for others. It highlighted a medical mystery: why are some people more fit to handle the flu than others?

British and American researchers think they have a clue. Reporting on Sunday in the journal Nature, researchers say they’ve found a gene that influences our susceptibility to flu illness. The gene, called IFITM3, is the “crucial first line of defense” against the flu, researcher Paul Kellam of Britain’s Sanger Institute told Reuters.

The IFITM3 protein prevents flu virusES from replicating in cells, sending them straight to waste disposal instead. So, if you have a high amount of IFITM3, you’re in luck, since it weakens the spread of the virus; a low amount can lead to more rapid viral replication, causing severe flu symptoms, according to Kellam.

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Scientists first found IFITM3 in gene studies that showed that IFITM3 played a role in resistance to flu and other viruses like dengue fever and West Nile virus. In subsequent experiments in mice, they showed that when mice were bred to lack the IFITM3 gene and then infected with influenza, the animals developed more severe respiratory and lung infection from flu, including pneumonia, compared with mice that had the gene.

To figure out the role of IFITM3 in humans, researchers then sequenced the IFITM3 genes of 53 patients who were hospitalized with the flu in 2009-10. They found that these patients were more likely to have a variant of the IFITM3 gene that codes for a shortened version of the protein — which makes people more vulnerable to flu — compared with the general population. According to evidence from large genetic databases, about 1 in 400 people carry this IFITM3 variant, the BBC reports.

“Our research is important for people who have this variant as we predict their immune defenses could be weakened to some virus infections,” said Kellam in a telephone briefing, the BBC reports.

The authors say that several factors, not just IFITM3, contribute to a person’s overall susceptibility to flu, but the findings suggest that it may be possible to screen people for the IFITM3 gene variant and pinpoint them for priority vaccinations or preventive treatments during flu epidemics. The findings also suggest that a drug that mimics IFITM3 could help increase resistance to flu and other viruses, including deadly ones like H5N1 avian flu.

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