Gov. Mike DeWine tested negative for the coronavirus hours after a positive rapid-result test prevented him from welcoming President Trump to Ohio on Thursday, reflecting the increasingly complex state of testing in the United States. The whiplash day of contradictory results is a further indication of the country’s limited ability to slow the spread of the virus with widespread and accurate testing. When Mr. DeWine was first tested on Thursday morning as part of a White House screening, he received an antigen test, a new frontier of testing that allows for results in minutes, not days, but has been shown...
