US Democratic Presidential candidate and former US vice president Joe Biden and his wife Jill Biden leave after the first presidential debate at Case Western Reserve University and Cleveland Clinic in Cleveland, Ohio, on Sept 29, 2020. (SAUL LOEB / AFP)

WASHINGTON - US Democratic presidential nominee Joe Biden and his wife, Jill Biden, have tested negative for COVID-19, his doctor said on Friday.

Thank you to everyone for your messages of concern. I hope this serves as a reminder: wear a mask, keep social distance, and wash your hands.

Joe Biden,  US Democratic presidential nominee 

"Joe Biden and Dr. Jill Biden underwent PCR testing for COVID-19 today and COVID-19 was not detected," Kevin O'Connor, the Bidens' primary care physician, said in a statement, referring to the polymerase chain reaction testing.

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Biden, 77, confirmed the negative results in a tweet later.

"Thank you to everyone for your messages of concern. I hope this serves as a reminder: wear a mask, keep social distance, and wash your hands," he wrote.

The couple took the tests hours after US President Donald Trump, whom Biden shared a stage with for the first 2020 presidential debate in Cleveland, Ohio Tuesday night, announced that he and his wife, Melania Trump, had contracted COVID-19.

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The presidential candidates did not shake hands that night. There was a distance between their podiums. But neither Biden nor Trump wore masks on stage.