By March 30, the overwhelming majority of U.S. states had issued stay-at-home directions — in many cases, those directions had already been in place for weeks. Which means that by April 30, one month later, anyone who had caught the disease before the lockdowns began should have already passed through the entire life cycle of the disease, either recovering or dying, and that all the new cases we are currently seeing are the result of infections since the shutdown. On April 30, after a month in which new cases ranged between 25,000 and 30,000, there were 29,500 new reported cases.

It is not entirely clear what accounts for this. It could be there is some feature of the disease we do not yet understand, or something about how long it incubates that we have failed to recognize. It is possible the disease remains infectious even after a patient has recovered, perhaps for a significant amount of time. It is possible that sheltering at home is a flawed quarantining method, since family members can infect one another, and that some meaningful share of the new cases come from within quarantines. It is possible that some meaningful share comes from within hospitals, with doctors and nurses and administrators all serving as vectors of the disease. It is possible that some meaningful share comes from the 50 million exposed frontline workers — employees at grocery stores and meat plants and pharmacies and the post office and so on — who are laboring (without hazard pay) to make the quarantines possible for the rest of us. Quite likely, a few of these factors, and possibly all, are contributing, to some degree (and 900 workers at a single Tyson Foods plant did just test positive). Together, they are preventing anything resembling a decline of deaths or cases as rapid as the ascent a month or so ago. Instead, under conditions that you might have thought — in theory — would bring the caseload close to zero in this amount of time, national deaths and caseloads have merely flattened out. Perhaps, depending on how you process the data, they’ve moved somewhat, but not dramatically, downward.