First lady Jill Biden has tested positive for COVID-19 again in what the White House is calling a "rebound" case.

"After testing negative on Tuesday, just now, the First Lady has tested positive for COVID-19 by antigen testing. This represents a 'rebound' positivity," the first lady's deputy communications director Kelsey Donohue said in a statement.

"The First Lady has experienced no reemergence of symptoms, and will remain in Delaware where she has reinstated isolation procedures. The White House Medical Unit has conducted contact tracing and close contacts have been notified," Donohue added.

Biden first tested positive for COVID on August 15 while on vacation in Kiawah Island, South Carolina. She was reported to have "mild symptoms" at the time and began isolating until she received two consecutive negative COVID-19 tests. Biden was prescribed the antiviral drug Paxlovid to treat her symptoms and had her second consecutive negative test on Sunday, when she traveled from South Carolina to meet President Joe Biden in Delaware.