The first US senator who tested positive for coronavirus has made a full recovery.

Republican Senator Rand Paul is volunteering with coronavirus patients at a local hospital after announcing on Tuesday that he had testing negative for Covid-19.

The 57-year-old, who tested positive on 22 March, faced criticism after it was reported he went swimming in the Senate gym and had lunch with lawmakers while awaiting his test results.

In a Twitter post, the Kentucky politician revealed he has left his self-quarantine to volunteer at TriStar Greenview Regional Hospital in Bowling Green.

"I appreciate all the best wishes I have received. I have been retested and I am negative," he said.

"I have started volunteering at a local hospital to assist those in my community who are in need of medical help, including Coronavirus patients. Together we will overcome this!"

While Mr Paul's infection was asymptomatic, he was tested in March out of an "abundance of caution" due to his extensive travel and event.

Following his positive test, Mr Paul – a medical doctor before going into politics – was criticised by colleagues for refusing to isolate himself while awaiting the results.

Senator Kyrsten Sinema, a Democrat from Arizona, said on Twitter that while she has "never commented about a fellow Senator's choices/actions," Mr Paul's actions were "absolutely irresponsible."

"You cannot be near other people while waiting for coronavirus test results," Ms Sinema said in the post. "It endangers others & likely increases the spread of the virus."

Mr Paul's positive diagnosis came days after his father -- former senator and presidential candidate Ron Paul -- suggested that the crisis was a hoax.

Ron Paul wrote on his website: "People should ask themselves whether this coronavirus 'pandemic' could be a big hoax, with the actual danger of the disease massively exaggerated by those who seek to profit -- financially or politically -- from the ensuing panic."

He referred to Dr Anthony Fauci, the health expert that has become the face of the administration's efforts to cope with the virus, as a "fearmonger."