WISCONSIN— Health experts continue to learn more about COVID-19 "long haulers." That's the informal term used to describe people who recovered from the virus but are still experiencing chronic symptoms, sometimes for months.

The scientific term is "post-acute COVID-19 syndrome." From what doctors know there are two main categories of "long haulers." 

Hospitalized patients with severe disease make up the biggest group. Dr. Aurora Pop-Vicas, an infectious disease specialist with UW Health, ​told us "about three-quarters of those are going to have some chronic symptoms that have to do with their hospitalization and recovery from the prolonged illness. They will leave the hospital with some amount of residual symptoms ..."

In the second group are patients who only had mild COVID-19 symptoms that did not require hospitalization or other critical medical treatments. 

"About 10% of those [patients] are likely to have some persistent residual symptoms waxing and waning, perhaps for weeks or months after their initial recovery," said Dr. Pop-Vicas.

The most common symptom that seems to be universally present is fatigue, which can be debilitating. Other common symptoms include the following: Chronic muscle pains, some joint pain, trouble sleeping, and maybe worsening depression or anxiety. Additional symptoms reported are things like shortness of breath, especially with exertion, and off and on chest pain. 

When it comes to recovering from the syndrome, Dr. Pop-Vicas said "it's a little bit early to tell exactly how the progression goes, from what we know from other respiratory illnesses in the past most, patients do recover gradually and over maybe prolonged time. We are still learning about a cohort of patients with "long COVID" ... and it will remain to be seen exactly how long the recovery takes."