It also provides another point of comparison to fellow coronavirus severe acute respiratory syndrome, or SARS, says Dr. Mark Denison, a pediatric infectious disease specialist at Vanderbilt University School of Medicine. SARS was “dramatically less common” among children than adults during the outbreak that began in China around 2003, and Denison says kids younger than 13 reported much less severe symptoms than older patients.

It’s possible that, due to some quirk of biology, children are simply less susceptible than adults to 2019-nCoV infection; their cells may be less hospitable to the virus, making it more difficult for 2019-nCoV to replicate and jump to other people, Denison says. The NEJM authors write that kids may be getting the virus but showing milder symptoms than adults, making them less likely to seek medical care and thus excluding them from research and case counts.

Denison says that tracks with the behavior of many other viral illnesses. “Evolutionarily, we’re designed to be exposed to these things as kids, and then we have broad-based immunity,” he says. “Get it now while you’re more likely to survive, and then you won’t get it later.”