Writing in her column in The Mirror, the former GMTV host detailed her symptoms including severe fatigue, a “fiery throat” and a persistent cough.
It took the 59-year-old three weeks to recover from the “scary” virus, which left her bed-ridden for days.
“All I can say is I felt as though I’d been clobbered in my sleep,” she explained.
“However hard I tried to get myself out of bed and on with the day ahead, something was holding me back.”
Describing the symptoms, Fiona said: “I’d had horrible gut pain for a few days.
“My whole digestive tract was making a pain of itself, demanding attention and really dragging me down.”
The star was still in bed three days after she first became ill and her husband – This Morning boss Martin Frizell – had to stay home from work to avoid the risk of infecting his ITV colleagues.
“Imagine how popular I’d have been if THAT had happened!” she said.
She added: “It was scary. It’s already caused untold death and destruction. And now it’s in your bed. In your body. Taking over your cells and all you can do is let it do what it does. Not knowing if it will. But terrified it might.
“And knowing there’s no cure. I didn’t let myself go there. So I slept. It’s all you can do. It’s all I felt like doing.”
The presenter confirmed she was now feeling better, though still tired, adding: “My thoughts very much remain with those still fighting this horrible disease.”
A number of high-profile stars have been affected by the pandemic, with Tom Hanks and Rita Wilson among the first to reveal that they’d tested positive for Covid-19, but have since recovered.
This article originally appeared on HuffPost.