“I leave the room and I can’t remember what the patient just said,” she said, adding that if she hadn’t exhausted her medical leave she’d take more time off.

“It scares me to think I’m working,” Ms. Mizelle, 53, said. “I feel like I have dementia.”

It’s becoming known as Covid brain fog: troubling cognitive symptoms that can include memory loss, confusion, difficulty focusing, dizziness and grasping for everyday words. Increasingly, Covid survivors say brain fog is impairing their ability to work and function normally.

“There are thousands of people who have that,” said Dr. Igor Koralnik, chief of neuro-infectious disease at Northwestern Medicine in Chicago, who has already seen hundreds of survivors at a post-Covid clinic he leads. “The impact on the work force that’s affected is going to be significant.