Jair Bolsonaro took his fourth test, on Monday after developing symptoms, including a high temperature. His previous three tests for the virus all came back negative.
Mr. Bolsonaro has repeatedly played down risks of what he has called the “little flu”, saying he would not be seriously affected. He has opposed lockdowns, which he says hurt the economy. He has since continued to rail against measures such as the closing beaches or requirements to wear face coverings.
Brazil has the second-highest number of Covid-19 cases and deaths in the world, after the US.
Mr. Bolsonaro said that he had started experiencing symptoms on Sunday. He said he had had a high temperature, a cough, and had felt unwell. He added that on Monday he had felt worse, which prompted him to take the coronavirus test.
The 65-year-old president is in a higher-risk group because of his age.
He said he was taking hydroxychloroquine – championed by US President Donald Trump – and azithromycin, an antibiotic, for days to treat the illness. Neither has been proven to be effective against the virus.
The executive director of the World Health Organization, Dr. Mike Ryan, wished President Bolsonaro “a speedy and full recovery from this disease”, adding: “I think the message to us all is: we are vulnerable to this virus.”
Back in April, President Bolsonaro said that even if infected, in quote “would not have to worry as I wouldn’t feel anything, at most, it would be like little flu or a little cold”.
The number of COVID-19-related deaths and infections – at that time under 3,000 and 40,000 – has since soared.
Despite this, President Bolsonaro has argued that regional lockdowns are having a more damaging effect than the virus itself, and accused the media of spreading panic and paranoia.
He has attended a number of public events without a mask, even when local rules required him to wear one.
On Sunday, Foreign Minister Ernesto Araújo posted a photo on social media showing himself with President Bolsonaro and others attending an Independence Day celebration at the US embassy in Brasilia. Nobody in the photo was wearing a mask or observing social distancing.
On Monday, he made further changes to a law that would require Brazilians to wear masks in public.