Various estimates project that 20% to 50% of COVID-19 patients go on to experience Long COVID. This has drawn attention to a similar condition called myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Dr. Jennifer Cope, an infectious disease specialist with the Centers for Disease Control and Prevention (CDC), recently explained some of the similarities and differences between the two syndromes.

What is ME/CFS?

ME/CFS is a complex, long-term health condition that affects up to 2.5 million people in the U.S. 

There is no specific tool or test to diagnose the condition, so it’s typically identified by the presence of a collection of symptoms. According to the 2015 case definition from the Institute of Medicine, ME/CFS includes:

• Limitations in daily activities due to extreme fatigue for six months or longer,
• Post-exertional malaise (PEM), which is the experience of excessive fatigue after a small amount of physical, emotional, or mental exertion, 
• Lack of improvement in symptoms after sleep, 
• Brain fog, and
• The inability to remain standing without worsening symptoms, also known as orthostatic intolerance.

What causes ME/CFS?

Like Long COVID, scientists aren’t sure what causes ME/CFS. 

“The cause – or causes – of ME/CFS are not known, and that is one of the more perplexing and frustrating aspects of this illness,” says Jennifer Cope, M.D., a medical officer with the Viral Disease Branch of the Center for Disease Control and Prevention (CDC). 

It’s thought to be a post-infection complication, but environmental pollutants, changes in the immune system, long-term stress, cellular defects, and a person’s genetics could also play a role. 

ME/CFS v. Long COVID

Cope says that Long COVID is used as a “broad, umbrella-like term” with different subgroups falling beneath it. Some people with Long COVID experience long-term complications, such as kidney damage, heart inflammation, or damaged lung tissue, which are easily detected through imaging and other tests.

Other COVID long-haulers, however, experience symptoms similar to ME/CFS, including PEM, brain fog, fatigue, orthostatic intolerance, headaches, and others that often occur without any detectable biophysical abnormalities. 

People with ME/CFS typically don’t fall into such different subtypes, Cope says. For example, PEM after COVID-19 could result from lung scarring and the development of chronic breathing difficulties, whereas ME/CFS-related PEM doesn’t usually stem from organ damage.

Cope also adds that while the loss of smell and taste is common among COVID-19 and Long COVID patients, it is typically not seen in people with ME/CFS.

*Cope, J., ME/CFS and Long COVID: Q&A With the CDC’s Dr. Jennifer Cope. (2022, November 17). Medscape. https://www.medscape.com/viewarticle/984122?icd=ssl_login_success_221201