Infectious disease mortality risk has a heritable component; children of parents who died of an infectious disease are ≈6× more likely to die of an infectious cause compared with the general population (2) . A recent large family study that used genealogic databases found an elevated risk for infl uenza death among relatives of persons who died of infl uenza (3) . By comparing the infl uenza mortality rate for relatives of persons who died of infl uenza with the infl uenza mortality rate for relatives of spouses of persons who died, the authors showed that the increased risk was not explained by shared exposure to infl uenza virus and thus may have a genetic component. However, to our knowledge, no published studies have examined the association between specifi c host genetic variants and severe infl uenza disease outcomes.