BARRIE, ONT. -- In the wake of the third wave of COVID-19, doctors say there's a new challenge emerging.

A recent study on COVID-19 long-haulers revealed many find fully recovering from the virus surprisingly elusive. More than 1,000 individuals across Canada participated in the study, which saw many continue to suffer from a wide range of persistent health problems, including headaches, fatigue and 'brain fog.'

"I've had patients who were previously high-functioning individuals, who now have trouble doing jobs and activities of daily living," says Royal Victoria Regional Health Centre (RVH) respirologist and intensive-care physician Dr. Adarsh Tailor.

Health experts say long-haulers experience symptoms for months after even mild cases of COVID-19.

"What we are starting to see in our clinics are people who had COVID three, four, five months ago who still have shortness of breath," Tailor says. "In my practice alone, I am probably seeing one to two of these patients daily."

Dr. Chris Martin, RVH critical care chief and director, says treating long-haul symptoms remains a bit of a mystery. "Can they be treated, or is it just a matter of time and supportive care?" he says further research will aid in caring for long-haul patients.

The Barrie hospital currently has 16 patients; most are no longer COVID-19-positive but remain sick enough to require hospital care, while the intensive care unit has eight patients battling COVID-19.

Dr. Martin says that while the overall number of COVID-19 cases declines across the province, there are still hundreds of ICU patients, some hospitalized for months.

The Canadian study estimates 25 to 35 per cent of individuals who test positive for COVID-19 experience long-term effects of the virus.