the 22-year-old posted.
Fellow US player Sachia Vickery responded on Saturday: "Now would be a great time to RIP this tweet for good..."
Tiafoe's announcement follows the slew of players who contracted Covid-19 after appearing at Novak Djokovic's exhibition event in the Balkans last month.
World number one Djokovic, Grigor Dimitrov, Borna Coric and Viktor Troicki all tested positive at an Adria Tour where social distancing was at a minimum, raising serious questions for professional tennis' return from lockdown in August.
Alexander Zverev, who tested negative in the Balkans, was then blasted as selfish for partying despite promising to self-isolate.
Organisers of the event in Florida reacted to Tiafoe's news on social media, saying that he and all the other players were tested on their arrival in Atalanta and subjected to daily temperature tests.
"Tiafoe has left the event site and will not participate in the remainder of the event. We will continue to diligently enforce all guidelines from local health officials."
The statement added: "Following his match (a win against Sam Querrey), he was showing symptoms and was retested and tested positive.
"Upon learning this information, we immediately began deep cleaning and sanitizing the event site, and enacted protocols in place for contact tracing and alerting individuals who may have been exposed."
The ATP Tour returns after its five month coronavirus hiatus with the behind closed doors Washington Open on 14 August, with the US Open at the end of the month.
Former Indian doubles player Mahesh Bhupathi voiced his dismay to the rising number of positive tests.
"When both common sense and logic go out the window, someone with some influence and authority needs to step up and say what's going on just needs to stop," he tweeted on Saturday.
"Sure everyone wants a pay day but this is poor leadership all round. 'safety first' RIGHT!!!"