A genetic variant frequently found in Chinese populations may explain why severe complications from swine flu are more common in China. The discovery may also have implications for other influenza virus strains and help scientists understand why flu outbreaks hit some populations harder than others.
The variant is an alternative form - an allele - of a key immune system gene. Chinese and British researchers looked for the variant in 83 patients admitted to a Beijing hospital during the 2009 and 2010 swine flu pandemic. The allele was found in 22 of the 32 patients who suffered severe complications from the virus but only 13 of the 51 patients with comparatively mild symptoms.
The scientists calculated that the variant increases the risk of developing a serious illness by five to six times once a person is already infected. The allele is found in around a quarter of Han Chinese, the largest ethnic group in China. It is also common among Japanese and Korean populations but found in only one in 3,000 caucasians.
'It doesn't mean you should panic if you have this gene variant', said Professor Sir Andrew McMichael, director of the Weatherall Institute of Molecular Medicine at the University of Oxford and one of the study's authors. 'Most people who have it won't run into any trouble at all'.
Previous research has shown that the variant – called rs12252-C – is associated with more severe disease for other kinds of flu. Although it doesn't make people more likely to catch the flu, it could help explain why new strains of the virus often emerge first in Asia. Swine flu swept around the world in 2009, infecting an estimated one in five people worldwide. Around 200,000 people died in the first year of the outbreak alone.
The latest results may lend support to the idea that genetic screening should eventually be included in national flu plans in order to better assess people at greatest risk of severe infection. Professor Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London, who was not involved in the study, told Associated Press: ' Further work needs to be done to justify that, but maybe in the future we would be able to say that if you're of a certain ethnicity, you are more at risk and should be prioritised for vaccination or antivirals'.
However, he added: 'It's possible we could one day do a genetic test before treating someone with flu to see what the best treatment would be'.
The study was published in Nature Communications.