those large aggregations—comprising bats that are more sedentary, more urban, less needful of flying long distances in search of wild food—tend to reinfect one another less frequently? And in the interim they accumulate more susceptible individuals? So when the virus does arrive, the spread of new infections is more sudden and intense? The virus is more prevalent and abundant? “Exactly. That’s it,” she said. “And then a great likelihood of spillover into another species?”