We conducted a hypothesis-generating pilot study to examine if host genetic variants were associated with fatal infl uenza virus infection by comparing prevalence of selected host genetic variants among children and A Pilot Study of Host Genetic Variants Associated with Infl uenzaassociated Deaths among Children and Young Adults 1 young adults who died of infl uenza with population-based prevalence estimates. We focused on 8 single-nucleotide polymorphisms (SNPs) in 2 candidate genes important in the innate immune response to infl uenza infection and for which national prevalence estimates were available: the gene for tumor necrosis factor superfamily, member 2 (offi cial symbol TNF) and the mannose-binding lectin gene (offi cial symbol MBL2).