Back in the 1980s, S.O.S. calls after midnight were common in the field of infectious disease. And as soon as my pager started to trill, I turned on my bedside lamp and dialed—often within thirty seconds. One night, I connected to an intern I’ll call Paddy. The background din quickly spelled “E.R.”

“Sorry to disturb you, Dr. P, but a woman woke with a rat on her face. Then the rat bit her lip.”

First, I expelled a disgusted “yecchh,” then I asked a question. “Was she drunk and passed o