The Bravo boss was originally supposed to host WWHL from home starting Sunday.
"After a few days of self-quarantine, and not feeling great, I have tested positive for Coronavirus," he wrote. "As much as I felt like I could push through whatever I was feeling to do #WWHL from home, we're putting a pin in that for now so I can focus on getting better."
He added, "I want to thank all the medical professionals who are working tirelessly for all of us, and urge everybody to stay home and take care of themselves."
The news comes only hours after Bravo announced Cohen would be filming "Watch What Happens Live" from his New York home starting Sunday. Guests including John Mayer, Jerry O'Connell and NeNe Leakes were to join him via video chat.
"Just when we thought our show couldn't get any more low-tech, we're all homebound," he said when the news was announced. "I'm not sure how this will play out, but I know it'll be fun."
According to his update, that will no longer be happening.