Brazilian President Jair Bolsonaro said he will know "in the next few hours" if he has contracted the new coronavirus after a top aide tested positive for the disease following a trip on which both met with US President Donald Trump.

The 64-year-old Bolsonaro revealed the news in a live Facebook transmission in which he was wearing a face mask, AFP reported.

"I'm using a mask because when we returned from our recent trip to the United States, one of the people that travelled with us had tests in Sao Paulo and it came up positive," said Bolsonaro.

The far-right leader's communications chief, Fabio Wajngarten, tested positive for COVID-19 after last weekend's trip to the US during which both men met with Trump at his Florida resort.

Wajngarten was photographed standing side-by-side with Trump.