From a Washington Post story by Toluse Olorunnipa headlined “Jill Biden tests positive for Covid, with ‘mild symptoms,’ White House says”:

First lady Jill Biden tested positive for the coronavirus on Monday, at the end of a three-day weekend she had spent alongside President Biden, the White House said.

“This evening, the First Lady tested positive for COVID-19,” Jill Biden’s communications director Elizabeth Alexander said. “She is currently experiencing only mild symptoms. She will remain at their home in Rehoboth Beach, Delaware.”

The president, who returned to Washington on Monday, took a coronavirus test and received a negative result after the first lady’s positive test, White House press secretary Karine Jean-Pierre said.