Modeling the course of the coronavirus pandemic may still be as much art as science as projections are shifting as more information becomes available. The good news is that conditions in most of the country are less dire than early models predicted, and public-health experts will have to study the reasons to help the country emerge from this economically destructive shutdown.

The so-called Murray model by the University of Washington’s Institute for Health Metrics and Evaluation on Tuesday projected 81,766 fatalities over...