Medical experts say there's no way to know for certain that someone is no longer contagious 10 days after testing positive.

US President Donald Trump holds a campaign rally on the South Lawn of the White House in Washington, October 10, 2020.
US President Donald Trump holds a campaign rally on the South Lawn of the White House in Washington, October 10, 2020. (AA)

US President Donald Trump is no longer a transmission risk for Covid-19.

White House doctor, Sean Conley, said on Sunday the president is looking forward to puttin his bout with coronavirus behind him and return to the campaign trail.

Trump, trailing his Democratic challenger Joe Biden in opinion polls, addressed supporters from a White House balcony on Saturday afternoon. 

He urged a crowd of hundreds of largely Black and Latino supporters to help get out the vote in the November 3 election.

Conley said in a statement later that Trump had taken a test on Saturday showing he was no longer "a transmission risk to others," and there was no longer evidence "of actively replicating virus."

But sensitive lab tests, like the PCR test cited in the doctor’s statements, detect virus in swab samples taken from the nose and throat. Dr. William Morice, who oversees laboratories at the Mayo Clinic, said earlier this week that using the PCR tests, the president’s medical team could hypothetically measure and track the amount of virus in samples over time and watch the viral load go down.

Some medical experts had been skeptical that Trump could be declared free of the risk of transmitting the virus so early in the course of his illness.

READ MORE: Trump back in Oval Office, says 'I feel great'

In rush to return campaign trail

Trump first revealed that he had tested positive on October 2, and spent three days in hospital. The White House has not disclosed when Trump last tested negative.

Trump is eager to get back on the campaign trail after an absence of more than a week. 

He plans to travel to the key battleground state of Florida on Monday, followed by rallies in Pennsylvania and Iowa on Tuesday and Wednesday, respectively.

"I'm feeling great," he told the crowd.

The president's illness has cast a spotlight on the pandemic, which has infected nearly 7.7 million people in the United States and killed over 213,000. 

His administration has faced criticism for its handling of the crisis, and for its lax approach to mask-wearing and social distancing in the White House. 

At least 11 close Trump aides have tested positive for coronavirus.

READ MORE: 'Don't be afraid,' Trump says of virus spreading through US and White House

Harsh criticism over WH gathering

Speaking firmly and with no sign of the raspy throat evident in recent interviews, Trump delivered a shorter-than-usual campaign speech.

He attacked Democrats as pursuing a "socialist" or even "Communist" agenda, and hailed his own record in fighting crime and boosting the US economy, while flag-waving supporters cheered and chanted, "We love you."

Democrats and some commentators criticised Saturday's event for potentially exposing a new batch of supporters to the virus and for using a federal building as an election prop.

Asked about it in New Castle, Delaware, Biden said he hoped the president and his supporters were taking precautions.

"They should be socially distant and wearing masks," he said. "It's the only responsible thing to do."

Trump standing alone at the event, was not wearing a mask as he spoke. In the crowd, most were wearing masks but not following social distancing guidelines.

Trump repeated past calls for states to reopen their economies even as new cases hit a two-month high on Friday. A Reuters analysis showed more than 58,000 infections were reported and hospitalisations in the Midwest hit a record for a fifth successive da y.

Opinion polls show Biden with a substantial lead nationally, although with a narrower advantage in some of the states that may decide the election outcome.

READ MORE: Trump halts virus relief package talks with Democrats until after election

Source: TRTWorld and agencies