The former gymnast shared the news on Instagram and admitted she was nervous and scared.

"Got my results back today and they came back positive for COVID," wrote the 29-year-old American before outlining her concerns.

"Not going to lie, I’m nervous knowing I’m positive.

"My body is just exhausted.

"1: I don’t want to get my family sick.

"2: I have asthma and have had it my entire life so this scares me a little extra.

"3: [I] had a very close family member fight for his life last month while battling COVID so it’s a serious topic of concern/hits home in our household."

Johnson, who claimed gold as well as three silver medals at Beijing 2008, said she had a "cough, terrible sore throat and a headache" along with "fatigue", although she felt pregnancy was a contributing factor.

"Not looking for any kind of pitty party," the three-time world champion, who retired in 2012, said in a separate post.

"Just a reminder to take care of yourself."

Johnson and her husband Andrew East announced they were expecting their second child earlier this month.

East tested positive for COVID-19 before Johnson caught the virus.

During her career, Johnson won all three of her world titles in 2007 - the same year she clinched four gold medals at the Pan American Games.

Her last major medals came at the 2011 Pan American Games, where she earned team gold and uneven bars silver.