Olympic 100m champion Noah Lyles feels testing positive for COVID-19 "definitely" affected his performance in Thursday's 200m final, as he was denied a sprint double by Letsile Tobego.

Lyles took gold in Sunday's 100m showpiece by five-thousandths of a second and had the chance to become the first man to win a 100m and 200m double at a single Olympics since Usain Bolt in 2016. 

However, he finished third behind Botswana's Tobego and fellow Team USA star Kenneth Bednarek, managing a time of 19.70 seconds at the Stade de France.

Tobego managed a 19.46 as he became Botswana's first Olympic gold medallist in any sport, handing his country just their third Olympic medal of any description.

Lyles appeared lethargic and was wheeled away from the track in a chair after the race, as rumours swirled regarding his health.

US Track and Field subsequently confirmed he had competed despite testing positive for COVID-19, and Lyles was proud of the way he fought through illness to take bronze.

"I do have Covid. I tested positive around 5am on Tuesday morning," Lyles told reporters after the race.

"I woke up in the middle of the night feeling real chills, aching, sore throat, and those were a lot of the symptoms I've had right before getting Covid.

"It definitely affected my performance. I've had to take a lot of breaks… I was coughing through the night.

"I'm more proud of myself than anything, coming out here to get a bronze with Covid. I've had better days, but I'm walking around again. I was quite light-headed after that race.

"Shortness of breath, chest pain, but after a while I could catch my breath and get my wits about me. I'm a lot better now."