Those looking for good news at the outset of the third wave do have something to point to: the lethality of the disease. Thanks to some combination of the age distribution of cases, improved treatments and better understanding of the disease, more vigilance in protecting the country’s most vulnerable, and more widespread mask-wearing, which can reduce the viral load of any exposure and thereby perhaps the risk of infection, the COVID-19 fatality rate appears much lower than it was in the spring. While the real fatality rate is a matter of some dispute and contestation, in August, Youyang Gu, then the pandemic’s most accurate modeler, calculated that it had fallen to 30 percent of its first-wave peak.

When I spoke to Gu in September, shortly before he discontinued his forecast citing exhaustion and the improved quality of other projections, he was relatively downbeat looking forward into the fall. While the disease’s estimated infection fatality rate remains dramatically lower than it was in the spring, he said he believed that was largely due to the age distribution of cases, and, less significantly, breakthroughs in treatment. It was likely just a matter of time, he said, before the rate creeps back up again.

Harvard’s Mina agrees, calling the possibility that the fall and winter could make the coronavirus not just more infectious but more lethal “likely,” and citing a variety of possible explanations: that our epithelium is dryer in the winter; that we produce less mucus; that the air both indoors and outdoors is dryer, then, too; and that there may be a seasonal effect on the viral load as well, meaning the body would produce more virus in the winter than in the summer, making it both more easily transmitted and more dangerous. The science of these dynamics in other diseases is not all that well-established, he cautioned, but suggested that it may very well be the case that many diseases we think of as “seasonal” are in fact year-round diseases which only get severe enough that we notice them in winter time.