Italian swim star Federica Pellegrini announced on Thursday that she has tested positive for coronavirus.
"I have just received the bad news," Pellegrini, 32, said in a video post on Instagram.
"This afternoon I had a swab and the result is positive. I am positive for the Covid."
Pellegrini won 200m freestyle gold at the 2008 Beijing Olympics, and is the world record holder over the distance.
She also won silver in the 200m freestyle at the 2004 Athens Olympics, and was targeting a fifth Summer Games in Tokyo.
"Yesterday I left a training session because I was in a lot of pain," said the former six-time world champion.
"Back home in the afternoon I started to have a sore throat, and obviously I didn't go back to the pool."
Pellegrini said she would not be competing in the International Swimming League (ISL) event in Budapest next week.
"I'm so sorry I couldn't wait to restart a normal season. I do not know whether to laugh or cry, in truth I have cried until now."