LONDON – A genetic variant commonly found in Chinese people may help explain why some became seriously ill with swine flu, a discovery scientists say could help pinpoint why flu viruses hit some populations particularly hard and alter how they are treated.
Less than 1 percent of Caucasians are thought to have the gene alteration, which has previously been linked to severe influenza. Yet about 25 percent of Chinese people have the gene variant. It is also common in Japanese and Koreans.
British and Chinese researchers analyzed 83 patients admitted to a Beijing hospital during the 2009-2010 swine flu pandemic. Of those with serious complications, such as pneumonia, respiratory or kidney failure, 69 percent had the genetic alteration. Among patients with mild illness, the figure came to only 25 percent.
“It doesn’t mean you should panic if you have this gene variant,” Andrew McMichael, director of the Weatherall Institute of Molecular Medicine at Oxford University and one of the study’s authors, said Tuesday. “Most people who have it won’t run into any trouble at all.”
He suggested that people with this genetic predisposition to severe flu should be treated earlier and more aggressively than others.
McMichael estimated that people with the genetic variant are five to six times more likely to become severely ill once infected. The gene alteration doesn’t make people more likely to catch the flu, since that depends on other factors like environmental exposure and previous immunity.
He said the gene variant might give people the same susceptibility to suffer severe illnesses from other ailments including dengue, SARS and other flu strains. But it could also provide them with better immunity if they recover. The research was published online Tuesday in the journal Nature Communications.
Some experts said it is an intriguing finding that shows a patient’s response to a virus may determine how sick they will become.
“The bug in someone who gets severely ill is not any different than the one that infects someone who has mild illness,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. “It’s the host that does all the damage to themselves.”
If people carry the genetic variant, Osterholm said, their immune systems are more likely to kick into overdrive if they catch the flu, blocking their airways or even causing organ damage.
Scientists have long recognized that diseases don’t strike all populations equally. Osterholm warned that the genetic variant isn’t limited to people of Chinese descent, saying, “A lot of other populations have the same genes that respond immunologically like this.”