Chinese people carrying a particular version of an immune system gene are up to six times more likely to develop severe influenza than those lacking the variant. In a previous study involving mostly people of European descent, scientists found that a few individuals carried a particular form of a gene known as IFITM3 and got hit especially hard by the flu. In China, the variant is much more common. About three-quarters of people carry at least one copy of the form of IFITM3 that is rare among Europeans, Tao Dong of Capital Medical University in Beijing and Oxford University in England and her colleagues have discovered. The researchers studied 83 people who were hospitalized with the H1N1 flu virus in 2009. Of the 35 people in that group who had two copies of the variant, 22 developed pneumonia or other severe flu symptoms, the researchers report online January 29 in Nature Communications.