LONDON A genetic variant commonly found in Chinese may help explain why some got seriously ill with swine flu, a discovery scientists say could help pinpoint why flu viruses hit some populations particularly hard and change how they are treated.
Fewer 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 have the gene variant, which also is common in Japanese and Koreans.
British and Chinese researchers analyzed 83 patients admitted to a Beijing hospital during the 2009-0 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, only 25 percent did.
It doesnt mean you should panic if you have this gene variant, said Andrew McMichael, director of the Weatherall Institute of Molecular Medicine at Oxford University, one of the studys authors. Most people who have it wont run into any trouble at all.
He suggested 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 were five to six times more likely to get severely ill once theyre infected. The gene alteration doesnt make people more likely to catch the flu, because that depends on other factors such as environmental exposure and previous immunity.
McMichael said the gene variant might give people the same susceptibility to get severely ill from other ailments including dengue fever, SARS and other flus.
But it also could provide them with better immunity if they recover.
The research was published online Tuesday in the journal Nature Communications.
Some experts said it was an intriguing finding that shows a patients 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, who did not participate in the study. Its the host that does all the damage to themselves.
If people carried the genetic variant, Osterholm said, their immune systems were more likely to kick into overdrive if they caught the flu, causing problems like organ damage or blocking their airways.
Scientists have long recognized that diseases dont strike all populations equally. Caucasian people are more likely to get the crippling Guillain-Barre syndrome after vaccinations and flu epidemics are often more fatal in indigenous populations in Australia and Canada. Records are too limited to know if previous flu outbreaks have been more lethal in Asia.
Osterholm warned that the genetic variant wasnt limited to people of Chinese descent. A lot of other populations have the same genes that respond immunologically like this, he said.
Osterholm thought that different flu strains would likely trigger different responses in people and just because Chinese may have been more vulnerable to severe illness with swine flu doesnt mean they would have the same reaction with other flus.
Others said genetic screening might one day be included in national flu plans.
Further work needs to be done to justify that, but maybe in the future we would be able to say that if youre of a certain ethnicity, you are more at risk and should be prioritized for vaccination or antivirals, said Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London. Its possible we could one day do a genetic test before treating someone with flu to see what the best treatment would be.