Genetic variant is associated with severe flu in the Chinese population

Researchers have found that two out of three patients in China with a severe influenza infection have a genetic variant of the IFITIM3 gene, previously shown to affect the severity of influenza infection in patients in the UK. By contrast, only one in four people in China with mild influenza have this genetic variant.

This variant is more common in the Chinese population compared to Northern Europeans and is associated with the severity of influenza infection rather than susceptibility to the disease.

IFITM3 is an important protein that can efficiently restrict the entry of influenza and other human viruses such as coronavirus, Dengue virus and West Nile virus into human cells. A genetic variant of this gene, rs12252, reduces antiviral activity of IFTIM3 leading to a more severe infection.

"Professor Paul Kellam at the Sanger Institute in Cambridge and Professor Peter Openshaw at Imperial College London discovered this genetic variant was associated with severe influenza infection in Europeans, but this variant is extremely rare in Europeans," says Dr Tao Dong, Lead author from the MRC Human Immunology Unit, Oxford University. "We became interested in this because we noticed it is 100 times more common in China.

 "It's vital that we continue to fund research that examines flu from the smallest details of our genetic code and in the populations around the world that continue to be vulnerable to infection."

The team examined samples from the 2009 H1N1influenza A pandemic in China. They found a strikingly large number of patients with severe influenza infections, had a CC genotype, or copies of the variant on both chromosomes. People with this CC genotype have a six-fold greater risk of severe infection compared to people with other genotypes, or different genetic makeup.