In infectious disease research, most of the research into genetic determinants of susceptibility to infection and disease severity are focused on the host. For COVID-19, for example, the delta variant’s infectivity, and how likely infection is to lead to severe disease, is the focus of an intense research agenda. But host genetics, too, contribute to the consequences of infections. An ongoing study into the host genetics of SARS-CoV-2 infection has identified 13 such factors that affected either the likelihood of contracting SARS-CoV-2, or the severity of disease, gleaned from the data of 50,000 infected persons and 2 million controls.