On Tuesday, Sept. 8, fitness entrepreneur Jillian Michaels, 46, opened up about her battle with COVID-19 in an interview with Fox Business.

While talking about her new Jillian Michaels Fitness App, the fitness instructor revealed she had fallen ill weeks prior when she contracted COVID-19 from a close friend.

"If you are afraid of COVID you should not go to the gym and I am actually a person who let their guard down — I haven't even spoken about this publicly really — and a very close friend of mine gave me COVID several weeks ago," said Michaels.

Her friend was unaware she had coronavirus when she came in contact with The Biggest Loser alum and Michaels had "no idea" she had it for six days.

"I am fortunate to have gone into it being healthy and I was able to get on the other side of it pretty quick but not everybody is that lucky, as we know," explained Michaels.

A majority of states have reopened public gyms with strict guidelines and safety measures are in place such as mask-wearing, sanitation stations, and more.

Michaels warns, "If you are afraid of getting COVID a public gym is probably a place you will get it and I would love to tell you that's not the cast but the reality is I literally let my guard down for an hour with one of my best friends who does my hair and makeup and I got it. It's just that simple."

Jillian Michaels is not the only celebrity to have suffered from coronavirus. Last week, on Sept. 2, Dwayne "The Rock" Johnson shared in an Instagram video that his family had fallen ill. "My wife Lauren as well as my two baby girls and myself, we have all tested positive for COVID-19," he said in the video. "And I can tell you that this has been one of the most challenging and difficult things we have ever had to endure as a family and for me personally too."

Michaels concluded the interview with Fox Business by wishing everyone to "Be safe, keep your guard up."