Rudolph W. Giuliani, former Mayor of New York City and personal attorney for President Trump, has tested positive for the corona virus, Trump announced on Twitter on Sunday.

“@RudyGiuliani, by far the greatest mayor in NYC history, and who has worked tirelessly to uncover what is by far the most corrupt elections in US history, tested positive for the China virus. Get well soon, Rudy, we carry on !!! “Mr. Trump wrote.

Mr. Giuliani was at Georgetown University Medical Center, according to a person who was aware of his condition but was not allowed to speak publicly.

Mr Giuliani has been exposed to the virus through contact with infected people, including while preparing Mr Trump for his first debate against President-elect Joseph R. Biden Jr. in September, just before the President tested positive and when he appeared with his son Andrew at a press conference at the headquarters of the Republican National Committee about two weeks ago. Andrew Giuliani, who works as a White House assistant, said Nov. 20 that he tested positive days after Donald Trump Jr.

It was unclear why Mr. Trump announced it. It was also unclear whether Mr Giuliani, 76, is symptomatic. However, at his age, he is in the high risk category for the virus.

Mr. Giuliani was the lead attorney for Mr. Trump’s efforts to overturn the election results. He has repeatedly alleged that he had evidence of widespread fraud, but has refused to provide that evidence in legal cases he has filed.

His infection is the last in a series of outbreaks among those in orbit of the President. Boris Epshteyn, a member of the Trump campaign legal team, tested positive late last month. On the same day, Mr. Giuliani attended a meeting of Republican legislators in Pennsylvania over allegations of electoral irregularity. One of the lawmakers at that meeting was informed shortly after at the White House that he had tested positive.

Mark Meadows, the President’s Chief of Staff, and at least eight other members of the White House and Mr Trump’s circle tested positive in the days before and after election day.

Mr Trump was hospitalized on October 2 after contracting the coronavirus. Kayleigh McEnany, the president’s press secretary, Corey Lewandowski, a campaign advisor, and Ben Carson, the housing secretary, are among those among the president who tested positive this fall.

Mr. Giuliani appeared on Fox News on Sunday. Speaking to host Maria Bartiromo over satellite, Mr. Giuliani repeated unsubstantiated allegations of fraud in Georgia and Wisconsin in Sunday Morning Futures. When asked if he believed that Mr. Trump still had a way to win, he said, “We will.”