Three years in, scientists still aren’t quite sure why some people get stuck with the syndrome and its cluster of debilitating symptoms long after their COVID-19 infection has cleared, while others breeze through and quickly return to a normal life.

In part, that’s because long COVID is so hard to pin down. For some patients, the main symptom is fatigue; for others, heart and respiratory problems. Still others may have frequent headaches, trouble sleeping, loss of taste, stomach pain, rash, muscle aches, or changes in menstrual cycles—or maybe a mix of symptoms. One patient may have a few annoying complaints for a couple of weeks, a second seemingly permanent discomfort.

There’s no simple formula for diagnosing patients, no test to tie symptoms to COVID-19, no pill to pop to make everything go away. Scientists and the public can’t even agree on what to call it: take your pick from long COVID, post-COVID conditions, long-haul COVID, post-acute COVID-19, post-acute sequelae of SARS CoV-2 infection, and chronic COVID.

Because it’s so difficult to diagnose, it’s also tough to figure out how many people have had it, but the Centers for Disease Control and Prevention suggests about 15% of all Americans have suffered from long COVID and that about 6% currently have it.

At the Boston University Chobanian & Avedisian School of Medicine and its primary teaching hospital, Boston Medical Center (BMC), researchers and clinicians are trying to decode long COVID.

As well as treating patients through the ReCOVer Long COVID Clinic, they’re leading the National Institutes of Health-funded RECOVER (Research COVID to Enhance Recovery) Long COVID Study, an effort to better understand the condition and pioneer new prevention and treatment approaches.

Here, Jai G. Marathe, assistant professor of medicine at Boston University and Boston Medical Center infectious diseases physician, and Fitzgerald Shepherd, assistant professor of general internal medicine and Boston Medical Center hospitalist, break down what they’ve learned about long COVID since starting the study last year.

Read the full article about long COVID by Andrew Thurston at Futurity.