By one estimate, there could be as many as ten million Americans suffering from long COVID-19. They have symptoms months, or even years, after getting infected.
Fifteen months ago, Caitlin Barber, who first had COVID in March, 2020, thought she had turned a corner. Her long COVID was improving.
But the 29-year-old from the Hudson Valley in New York state has regressed.
"I have trouble just doing daily tasks at this point," she said.
Barber told WCBS 880 in March, 2021, that she was "slowly recovering and making a lot of progress," but she now describes her healing as "unpredictable."
"Recovery is not just a straight up diagonal line," she said. "There are many bumps in the road."
She has faced severe depression, and walking became a problem again.
"There's a huge question in my mind of [whether] this [will] be the rest of my life or not," Barber said.
Barber's post-COVID story is common, but the cause is still a mystery.
Zijian Chen, Barber's doctor and director of the Mt. Sinai Hospital Post-COVID Center in Manhattan, said his department is still working to help patients recover.
"We're trying different treatment algorithms to see whether one thing works better than the other," he explained. "And then, over time, [refine] what we do."
Chen added that there are a lot of theories, including studies looking at different ways COVID can cause initial changes to the body.