Researchers in Argentina used existing mathematical models of how colonies of head lice (Pediculus humanus capitis) grow and spread, based on laboratory studies, and matched them up with analysis of lice infestations in children in real-world classrooms. What they found suggests that head lice infestations across a classroom likely require the presence of at least one severely infested child, playing the role of “superspreader.” (Photo credit: Mohammed El Damir, Bugwood.org)