Covid-19 Ranged From Illinois to Massachusetts Before States Reported First Cases

The Covid-19 virus infected people in five U.S. states in December 2019 and early 2020 before those states reported their first cases, according to a large new government study, providing new insights into the first, unseen weeks of the nation’s deadly epidemic.

Scientists analyzing blood samples taken for a National Institutes of Health research program identified seven people in states from Mississippi to Wisconsin to Pennsylvania who were infected with the new virus days or weeks before the first cases were confirmed in their areas. At least a couple had mild symptoms.

Their...