Nonstop inflammation and immune problems top the list of potential causes of long COVID, but doctors say it's growing clear that more than one thing is to blame for the wide swath of often debilitating symptoms that could last months or even years.
"I think that it's a much more complex picture than just inflammation, or just autoimmunity, or just immune dysregulation. And it's probably a combination of all three causing a cascade of effects that then manifests itself as brain fog, or shortness of breath, or chronic fatigue," says Alexander Truong, MD, a pulmonologist and assistant professor at Emory University School of Medicine, who also runs a long COVID clinic.
Long COVID, a post-COVID-19 condition, and post-acute sequelae of SARS-CoV-2 (PASC) are among the terms used by the National Institutes of Health (NIH) to describe the long-term health issues faced by an estimated 10% to 30% of people infected with COVID-19. Symptoms — as many as 200 — can range from inconvenient to crippling, damage multiple organ systems, come and go, and relapse. Long COVID increases the risk of worsening existing health problems and triggering new ones, including cardiovascular disease and type 2 diabetes.
So far, research suggests there is no single cause, condition, or disease that explains why some people have an extensive range of symptoms long after the early COVID-19 infection has cleared up. Many experts believe some combination of biological processes — including the virus hanging around in our bodies, inflammation, autoimmunity, tiny blood clots, immune system problems, and even the reactivation of dormant viruses such as the Epstein-Barr virus — could be the culprit, a theory also supported by a comprehensive and in-depth review of long COVID studies published in January in the journal Nature Reviews Microbiology.
