American First Lady Jill Biden tested positive for Covid, the White House said.
The 71-year-old had tested negative on Monday during a regular test session, but developed cold-like symptoms that evening.
She tested negative on a rapid antigen test before a PCR test was positive.
Spokeswoman Elizabeth Alexander said it, like her husband Joe Bidenthe first lady had two vaccinations and two booster vaccinations against the disease.
She has mild symptoms and has been prescribed the antiviral drug Paxlovid.
Mr. and Ms. Biden are on vacation in South Carolina. He will isolate himself there for at least five days, the White House said, and return home after two consecutive negative tests.
Mr. Biden caught the virus last monthbut experienced a rebound case days after testing negativewhich required a second period of self-isolation.
The president was also given Paxlovidwhich can reduce hospitalization and death among patients by 90% when administered within five days of onset of symptoms.
But it is also associated with a higher incidence of rebound infections, in which patients test positive again days after the drug helped them clear the initial infection.
Mr. Biden tested negative on Tuesday, the White House said, but will wear a face mask indoors for 10 days, in line with guidelines from the Centers for Disease Control and Prevention.
He went back to work.
