A charter staffer who was on board Democratic presidential nominee Joe Biden's campaign plane has tested positive for the novel coronavirus, the former Vice President's campaign announced.

The staffer flew with Biden to the state of Ohio on Monday and Florida on Tuesday, but they were always over 50 feet away from each other and wore masks, Xinhua news agency quoted the campaign as saying in a statement on Thursday.

The statement said the person who tested positive was an "administrative member" of the company that charters Biden's 737 aircraft but was in the last row of the plane and "did not even have passing contact" with the former Vice President.

"Given these facts, we have been advised by the Vice President's doctor and the campaign's medical advisors that there is no need for the Vice President to quarantine," campaign manager Jen O'Malley Dillon said in the statement.

Taking to Twitter on Thursday, Biden said: "Not only was the individual 50+ feet away and wearing a mask, but I was wearing an N-95 mask. No members of my staff were in contact with this crew member either. My doctors have advised that there is no need for me to quarantine.

"If anything, let this serve as an example of the importance of wearing masks and keeping a safe, social distance."

Earlier in the day, Biden's running mate Kamala Harris cancelled her campaign travel through this weekend after her Communications Director Liz Allen and a flight crew member both tested positive for Covid-19.

Both Harris and her husband Doug Emhoff tested negative for the virus on Thursday.

O'Malley Dillon said the Biden campaign has begun the process of contact tracing "to notify everyone who came into contact with the individuals during the potential infection window".