Like Novak Djokovic, the world No.1's wife, two other players and their coaches, Dimitrov contracted COVID-19 while playing in last month's Adria Tour exhibition series in Serbia.

The former world No.3 and Australian Open semi-finalist says the ordeal really shook him up and that he's still feeling the ongoing effects.

"(It's) still not easy to recover. The virus was hard on me. I stayed home for about a month," Dimitrov told Tennis Majors at the Ultimate Tennis Showdown (UTS) at the Mouratoglou Academy in France.

"I was not breathing well, I was not feeling well; tired. (I had) all the symptoms;, no taste, no smell, everything you could think of. So it was no fun."

Still feeling lethargic several weeks on and having lost three kilos, Dimitrov has lost both of his matches at the UTS to be last in his pool behind Richard Gasquet, Feliciano Lopez and Australian Alexei Popyrin.

"Lucky to be playing right now," said Dimitrov, adding that he was a doubtful starter for the US Open starting in a month.

A semi-finalist in New York last year after eliminating Roger Federer, Dimitrov said the whole experience, especially dealing with isolation, had been frightening.

"You're alone for about 20 days for 24 hours," the 29-year-old said.

"I spent over 5,000 hours by myself. A lot of things are going through your head.

"It doesn't matter how mentally strong you are as a person or athlete, it's inevitable to get some bad thoughts in your head. So I had to deal with that too, and so has everybody else out there.

"That's one of my biggest messages - we should not underestimate the power of the mental state that everybody is in.

"This thing is real. If we take the right precautions and everybody is safe, then things will get better quicker.

"But it's a strange time."

Australian Associated Press