World number one Novak Djokovic has tested positive for coronavirus, according to a statement published by Sport Klub.
Djokovic and his wife Jelena returned positive tests in Belgrade and must isolate for 14 days.
The 33 year-old was a driving force behind the creation of the Adria Tour, which took place in Serbia and Croatia in front of large crowds and saw players shaking hands despite concerns over social distancing.
The final between Djokovic and Andrey Rublev was cancelled when Grigor Dimitrov tested positive for COVID-19.
Borna Coric and Viktor Troicki, who both competed in the tournament, have also contracted the virus.
Kyrgios labelled the decision to go ahead with the tour as "boneheaded" after Coric's announcement of a positive test on Tuesday (AEST).
And, responding to a video showing Djokovic and others at the tournament partying shirtless together, Kyrgios directed further criticism at the 17-time grand slam champion.
He posted on Twitter: "Prayers up to all the players that have contracted Covid - 19. Don't @ me for anything I've done that has been 'irresponsible' or classified as 'stupidity' - this takes the cake."