US President Donald Trump's eldest son Donald Trump Jr has tested positive for Covid-19 and is quarantining without symptoms, the latest in a long list of infections among those with links to the White House.

“Don tested positive at the start of the week and has been quarantining out at his cabin since the result,” his spokesman said.

“He's been completely asymptomatic so far and is following all medically recommended Covid-19 guidelines,” the spokesman said of the 42-year-old.

Trump Jr's positive test follows infections for a string of others connected to the White House, including his father, who was hospitalised, the president's wife Melania and Trump's youngest son Barron, AFP reports.