Social context alters host behavior and infection risk

Variation in infection risk and transmission potential are widespread in human and wildlife diseases and play a central role in host-pathogen dynamics. To explain this variation, most studies focus on linking host traits to differences in pathogen exposure, infection, and transmission, but typically do not to account for hosts’ social context. Yet, an individual’s risk of acquiring infection is likely influenced jointly by their own traits and their social environment. Here, we use three natural genotypes of the fruit fly Drosophila melanogaster to test how variation in pathogen transmission is linked to differences in host behavior and social context. We constructed groups of 12 flies from one of three different genotypes and five different sex ratios (0%, 33%, 50%, 67%, or 100% female) in a fully factorial design. To each group we added a male or female “primary case” fly that had been exposed to the generalist fungal entomopathogen Metarhizium robertsii. We then recorded groups’ aggr...