The owner of Greek league leaders Olympiakos on Tuesday said he had coronavirus, two days before a Europa League clash with Wolves that is to be held behind closed doors.
Vangelis Marinakis, who is also the owner of English second-tier club Nottingham Forest, said he was taking "all necessary measures" and "feeling well".
"I am following the instructions of doctors. I strongly (advise) all my fellow citizens to do the same," Marinakis, 52, said on his Facebook page.
Greece has announced 89 cases of the virus, including a 66-year-old man with acute pneumonia whose condition is critical.
Most of the cases come from a single group of Holy Land pilgrims that travelled to Israel and Egypt last month.
Authorities have shut schools and cancelled public events in three areas in western Greece where the group had come from.
Dozens of schools in Athens and Thessaloniki have also been shut for two weeks.
The outbreak will also affect the Olympic Flame lighting ceremony for this summer's Tokyo Games, which will be held without spectators in ancient Olympia.
The Greek Olympic Committee on Monday said that only 100 accredited guests from the International Olympic Committee and the Tokyo 2020 Organising Committee will be allowed to attend Thursday's event in Olympia, where the ancient Games were held.
A dress rehearsal scheduled for Wednesday will also be closed to the public.
The health ministry on Monday also said that all professional sports events for the next two weeks will be played without spectators.
The measure will also affect postseason games in the Greek Super League play-offs, as well as those in basketball, handball and water polo.