A tennis ball covered in spikes. That’s all we’ve got. More than a year has passed since the first reports of human-to-human transmission of the novel coronavirus, and its most memorable visual signifier is a stylized illustration of the virus itself. That spiky ball floats in the background of explanatory graphics and charts, or looms eerily behind the heads of television anchors delivering yet more somber news. When I think of COVID-19, that’s what I see.

Psychiatric hospitals, nursing homes, and other long-term-care facilities have served as chilling backdrops to some of film’s most arresting psychological thrillers. But the foreboding lighthouse of Shutter Island and the macabre, labyrinthine hospital of One Flew Over the Cuckoo’s Nest pale in comparison with both movies’ animating horrors: the wretched treatment of the people trapped within.

On its face, reinfection appears to be a straightforward term. It is literally “infection, again”—a recovered person’s second dalliance with the same microbe. Long written into the scientific literature of infectious disease, it is a familiar word, innocuous enough: a microbial echo, an immunological encore act.But thanks to the pandemic, reinfection has become a semantic and scientific mess.

On a golden day last September, I visited the ruins of the first Greek city on the Iberian Peninsula, a settlement from the sixth century B.C. called Empúries. Traders venturing down present-day Spain’s Costa Brava, a rugged stretch of coastline in northeastern Catalonia, had recognized the advantages of the location: a natural port, some protection from the fierce tramontana winds blowing off the Pyrenees, and access to local trade networks established by native Iberians.