is there a relationship between that initial "dose" of virus and the severity of the disease—that is, does more exposure result in graver illness?...
Most epidemiologists, given the paucity of data, have been forced to model the spread of the new coronavirus as if it were a binary phenomenon: individuals are either exposed or unexposed, infected or uninfected, symptomatic patients or asymptomatic carriers.
Actually, though, "The doctor and medical researcher in me—as a graduate student, I was trained in viral immunology—wanted to know...what was the severity of disease in each case?"
The severity of the Covid-19 disease varies greatly, as another doctor put it recently, "ranging from life-threatening pneumonia to what seems like a really bad cold," a point that has been under-appreciated but, as Mukherjee argues, is relevant.
I hate to sound defensive or repetitive on this point, but, again, Mukherjee is not some crank libertarian blogger or Fox Business Channel anchor. This is a Pulitzer-prize-winning Columbia medical doctor, writing in the New Yorker, a mainstream, elite, liberal magazine. And, again, I hate to sound repetitive on this point, too—it doesn't mean that the case you get will be a less severe one, or that precautions are not necessary to avoid risk. Wash your hands, keep your distance, and if in doubt consult your doctor and or federal, state, and local authorities. But keep in mind, too, that the charts showing rising numbers of positive tests or new confirmed cases only tell part of the story. The severity of the cases matters, too.