There has been significant debate over many years as to why some people cope with infections better than others. In particular, influenza can exert its effects in a mild form or in a much more severe way. While this reflects a range of factors including the genetics of the virus (genetic drift and, more importantly, genetic shift), the residual immunity in the population at risk and underlying co-morbidities, the role that host genetics plays is relatively under-investigated. This paper uses a knockout mouse model to show that the interferon-inducible transmembrane (IFITM)...