While most patients affected by the A(H1N1) influenza pandemic (swine flu) experienced mild symptoms, a small fraction required hospitalization, often without concomitant factors that could explain such a severe course.

Scientists at the IBE (CSIC-UPF) leaded by Francesc Calafell, hypothesized that host genetic factors could contribute to aggravate the disease. To test this hypothesis, they compared the allele frequencies of 547,296 genome-wide single nucleotide polymorphisms (SNPs) between 49 severe and 107 mild confirmed influenza A cases.

They did not find significant associations for any SNP. Even though sample sizes were rather low, they allowed researchers to rule out that any major genetic factor could explain poor influenza A course.

Reference Article: Garcia-Etxebarria K, Bracho MA, Galán JC, Pumarola T, Castilla J, Ortiz de Lejarazu R, Rodríguez-Dominguez M, Quintela I, Bonet N, Garcia-Garcerà M, Domínguez A, González-Candelas F, Calafell F, on behalf of the CIBERESP Cases and Controls in Pandemic Influenza Working Group. No Major Host Genetic Risk Factor Contributed to A(H1N1)2009 Influenza Severity. PLoS ONE, 10(9): e0135983.