WASHINGTON, D.C. (WNCN) — President Joe Biden tested negative for COVID-19 Sunday morning for the second day in a row.

He tested negative Saturday morning, but continued to isolate at the White House until a second negative test, according to his doctor.

Dr. Kevin O’Connor wrote in Sunday morning’s daily update that the president “will safely return to public engagement and presidential travel.”

Biden, 79, came down with the virus a second time three days after he had emerged from isolation from his initial bout with COVID-19, reported on July 21.

During his first go-around with the virus, Biden’s primary symptoms were a runny nose, fatigue and a loose cough, his doctor said at the time. During his rebound case, O’Connor said only Biden’s cough returned and had “almost completely resolved” by Friday.

O’Connor wrote that Biden “continues to feel very well.”

The president plans to visit Kentucky on Monday to view damage from catastrophic flooding and meet with families.

There have been rare rebound cases documented among a small minority of those, who like Biden, were prescribed the anti-viral medication Paxlovid, which has been proved to reduce the risk of serious illness and death from the virus among those at highest risk.

Regulators are still studying the prevalence and virulence of rebound cases, but the Centers for Disease Control and Prevention in May warned doctors that it has been reported to occur within two days to eight days after initially testing negative for the virus.

“Limited information currently available from case reports suggests that persons treated with Paxlovid who experience COVID-19 rebound have had mild illness; there are no reports of severe disease,” the agency said at the time.