is a test case for this new model of thinking about infection as a trigger of immune dysfunction. One of the disease’s great mysteries is why some thirty-year-olds die from it and others don’t even notice they have it, while still others have a mild acute case but end up suffering from long COVID for months afterward, unable to walk up a flight of stairs without getting winded and dizzy. This pandemic has vividly dramatized the variability—and lingering complexity—of the human host’s response to a pathogen.
