As parents have long known, children in day care centers and schools readily spread respiratory diseases among one another. Chimpanzee communities seem to suffer in a similar way: playdates drive the dissemination of respiratory infections among the primates, according to a new study.

Scientists led by Hjalmar Kuehl and Peter Walsh of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, examined two chimpanzee groups in Taï National Park in Ivory Coast. Infants were more likely to die from a respiratory disease the more they played together—typically during the peak fruit season, when chimps congregate. Between the ages of two and three, chimps spend up to 18 percent of their day engaged in close physical contact with their peers. This period represents the peak of their social interaction and serves to connect all members of their community.

Once playful chimpanzees precipitated an outbreak, infants of all ages succumbed to disease. Affected mothers quickly entered into estrus, ultimately perpetuating the three-year cycle of infant population boom and bust. Coupled with poaching, climate change and predation, infant mortality from infectious disease is taking a toll on the area's chimps, says Kuehl, whose research findings appear in the June 18 PLoS ONE. These days few infants reach adulthood, he states, with “only four out of 10 surviving to the age of five.”