America should prepare for a double pandemic

A second virus would be especially devastating if it targeted a different slice of the populace than COVID-19. Unlike SARS-CoV-2, many respiratory viruses disproportionately affect children, and the 1918 flu pandemic was especially deadly for adults ages 20 to 40. “Something that decimates children or young people is a different ballgame,” says Zeynep Tufekci, a sociologist at the University of North Carolina and an Atlantic contributor. “It’d be economically devastating, and you’d no longer have an age group that’s protected.” The current debate about opening schools would be completely off the table. “In such a case, 1 plus 1 isn’t 2, but 10,” she adds.

It’s certainly possible for people to contract multiple respiratory viruses at once, and in early spring, some adults were indeed infected with both flu and SARS-CoV-2. But it’s hard to predict what happens when two severe pathogens hit the same person. Viruses reproduce by co-opting their host’s cells, and two of them might obstruct each other by competing for the same cellular machinery. It’s also possible that one would trigger a generic immune response, like inflammation, that would make it harder for the second to take hold. Then again, it’s also possible that two severe diseases would compound each other. “The knotty heart of all these problems is the immune system,” Metcalf told me, which is so complicated that trying to understand it, much less predict it, “is just miserable.”

Untangling those knots is especially hard in the midst of a pandemic. Currently, the scientific community is hell-bent on studying COVID-19, but basic questions remain unanswered. Why do some people get sick and others do not? What’s the full range of symptoms? Why do some people infect many while many infect no one? “Look at the energy it’s taking,” says Nahid Bhadelia, an infectious-disease physician at Boston University, “and the level of uncertainty” that just one new virus creates. Scientists, much like the health-care and public-health communities, are neither infinite nor indefatigable. A second virus would more than double their burden because they would have to analyze the diseases individually, as well as any interactions between them.