Republican Kentucky senator Rand Paul tests positive for COVID-19 and will remain in quarantine, according to his official Twitter account.

Sen. Rand Paul, R-Ky., was on the receiving end of withering criticism from Senate colleagues after it appeared he was still tending to his typical business at the U.S. Capitol after being tested for the coronavirus — his results came back positive Sunday.

Leading the charge was Sen. Kyrsten Sinema, D-Ariz., who tweeted Sunday in reaction to a report from The New York Times that Paul was at the Senate gym that same morning, apparently just hours before he learned he had tested positive for coronavirus.

"I’ve never commented about a fellow Senator’s choices/actions. Never once," she said. "This, America, is absolutely irresponsible. You cannot be near other people while waiting for coronavirus test results. It endangers others & likely increases the spread of the virus."

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Sinema sounded off as it became clear lawmakers on both sides of the aisle were angry with not just Paul for sticking around while awaiting the test results but with the decision for Senate Republicans to be consistently meeting in person over the past weeks as Democrats largely took care of their business via conference call.

"We need to talk with the Attending Physician," one senior GOP source said, referring to Dr. Brian Monahan, the Attending Physician for the Capitol. "And, Rand Paul."

Paul's office defended his actions Sunday as largely precautionary, implying the positive coronavirus diagnosis was a surprise.

"Similar to the President and the Vice President, Senator Rand Paul decided to get tested after attending an event where two individuals subsequently tested positive for COVID-19, even though he wasn't aware of any direct contact with either one of them," a statement from Paul Deputy Chief of Staff Sergio Gor said. "Additionally, due to a prior lung injury, and subsequent surgery on his lung, Senator Paul is in a higher risk category as it relates to pulmonary issues."

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A tweet from Paul's Twitter account further defended the Kentucky senator.

"We want to be clear, Senator Paul left the Senate IMMEDIATELY upon learning of his diagnosis," it said. "He had zero contact with anyone & went into quarantine. Insinuations such as those below that he went to the gym after learning of his results are just completely false & irresponsible!"

But the criticism of the senator largely focused on his call not to self-quarantine while awaiting the test result.

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Paul did have one high profile supporter amid the chorus of criticism he faced Sunday — President Trump.

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"My friend (always there when I’ve needed him!), Senator @RandPaul, was just tested 'positive' from the Chinese Virus. That is not good! He is strong and will get better. Just spoke to him and he was in good spirits," Trump said.

Paul's office has said that he is in quarantine in Kentucky while continuing to work and that he has not shown any symptoms from the coronavirus. It also said that his D.C. staff had been working remotely for the past 10 days. Paul is one of five Senate Republicans in quarantine right now — meaning Republicans only hold a 48-47 Senate majority among those capable of voting in person as lawmakers try to hash out a coronavirus stimulus package.

Fox News' Chad Pergram and Ronn Blitzer contributed to this report.