On Tuesday, world number one Novak Djokovic tested positive for coronavirus.
He had recently played in a tennis exhibition series in Serbia and Croatia which he had organised.
The top-ranked Serb played in Belgrade and then in Zadar, Croatia. His wife has also tested positive. Viktor Troicki, Grigor Dimitrov and Borna Croic are the three other tennis players who have tested positive to the virus.
Djokovic has been heavily criticised for organising the tournament, which observed very little social distancing measures, during the coronavirus pandemic. The tournament also brought in players from other countries. The opening round featured packed stands, players hugging at the net, playing basketball, posing for pictures and attending press conferences together. Videos had also surfaced of players dancing bare-top in a nightclub.
"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," Djokovic said in a statement.
"Everything we did in the past month, we did with a pure heat and sincere intentions.
"Our tournament meant to unite and share a message of solidarity and compassion throughout the region."
Djokovic was the face behind the Adria Tour and has since defended his actions after his positive test result.
"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 said.
"We organised the tournament at the moment when the virus has weakened, believing that the conditions for hosting the Tour had been met.
"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 with 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."
Djokovic has apolgised for anyone who gets infected as a result of the Tour and says he will remain in self isolation for 14 days.