PITTSBURGH (KDKA) -- Wayne Grabiak was in the hospital with COVID-19 for 10 days in late October. He almost ended up on a breathing machine.

"I had a few scary days that I definitely did not think I was going to make it," Grabiak said. "I had literally picked up my phone to text my siblings to tell them I thought this was checkout time. Thank God that I'm still here."

While he survived, he has had weeks of symptoms. His doctors told him he should feel better by the end of November. Then the end of December.

"It has definitely hung on," Wayne says.

Up to 10 percent of people have persistent problems that interfere with day-to-day function, even three to six months later.

"Cough, shortness of breath and fatigue." Dr. Marc Itkowitz, a primary care internist at Allegheny Health, said. "I have approximately five to 10 patients that I've been monitoring weekly and now monthly."

And it's not necessarily people who were in the ICU.

"What we're finding is that young adults, ages 20 to 40 who had a relatively mild acute course, are the most likely to report chronic symptoms," says Dr. Itskowitz.

Treatment is mostly supportive.

"We certainly look at a chest x-ray and look to see if they need antibiotics. But generally, the albuterol inhaler, the inhaled steroids are some of the more common medications we're using for these patients," Dr. Itskowitz said.

Researchers are still trying to figure out why some people become the so-called "long-haulers."

"We know that this virus has a significant propensity to activate the immune system," said Dr. Itskowitz. "In some patients, this immune activation can lead to what we call autoimmune disease, where the body's immune system is generating antibodies against its own self."

This could explain some of the chronic symptoms and leads to treatments targeting these autoimmune antibodies. For now, supporting patients until they get better is the approach.

"Most patients make a full recovery after a few weeks," Dr. Itskowitz says.

"By now, I thought it would be gone, and I would be back to 100 percent," Wayne says. "I think that would be a good idea if they did have a clinic that people who are experiencing things longer than what they expected could go and speak with someone."

For patients like Wayne, clinics for long-haulers are springing up around the country.