World number one Novak Djokovic has tested positive for coronavirus.
The 33-year-old and his wife Jelena returned positive tests in Belgrade after returning from the curtailed Adria Tour, while his children tested negative.
The 17-time grand slam singles champion is asymptomatic and will now isolate for 14 days.
"The moment we arrived in Belgrade we went to be tested. My result is positive, just as Jelena's, while the results of our children are negative," a statement from Djokovic via the Adria Tour's Instagram account read.
"Everything we did in the past month, we did with a pure heart and sincere intentions. Our tournament meant to unite and share a message of solidarity and compassion throughout the region.
"The Tour has been designed to help both established and up and coming tennis players from south-eastern Europe to gain access to some competitive tennis while the various tours are on hold due to the COVID-19 situation.
"It was all born with a philanthropic idea, to direct all raised funds towards people in need and it warmed my heart to see how everybody strongly responded to this."
Djokovic 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.
However, the final between Djokovic and Andrey Rublev was cancelled when Grigor Dimitrov tested positive for COVID-19 and Borna Coric later confirmed he too had contracted coronavirus.
Viktor Troicki, who played in the tournament in Belgrade, and his wife also tested positive for the virus.
The decision to hold the event during the pandemic has been criticised by Tour players including Nick Kyrgios and Dan Evans, while long-term rival and friend Andy Murray described the fall-out as "a lesson for all of us".
"We organised the tournament at the moment when the virus has weakened, believing that the conditions for hosting the Tour had been met," Djokovic said.
"Unfortunately, this virus is still present, and it is a new reality that we are still learning to cope and live with.
"I am hoping things will ease in time so we can all resume lives the way they were.
"I am extremely sorry for each individual case of infection. I hope that it will not complicate anyone's health situation and that everyone will be fine.
"I will remain in self-isolation for the next 14 days, and repeat the test in five days."