Covid Tally Baffles Scientists Struggling With Muddy U.S. Data (1)

In early January the state of Massachusetts added a new set of figures to its Covid-19 dashboard. Two years into the pandemic, it began to draw a distinction between people who were hospitalized because of the virus and people who were there for other reasons but also happened to be infected.

Nothing changed inside the hospitals’ walls—a Covid-positive patient there because of a car crash still had to be isolated. But the effect on the state’s numbers was dramatic. It cut them in half.

While cases have plunged and the death tally is slowing, the U.S. will in the ...