So did Boris Johnson, who announced his positive test on March 27 in a Twitter video which showed him perfectly lucid and without noticeable symptoms [1]. He posted regular video updates, appearing quite healthy in all of them, but his condition suddenly worsened on April 6, a full 10 days after his initial announcement video [2].

This is anecdata, of course, but Bolsonaro is 65, a full 9 years older than Johnson, so he's by no means in the clear.

[1] https://twitter.com/BorisJohnson/status/1243496858095411200

[2] https://www.theguardian.com/world/2020/apr/05/timeline-boris...