Five things to know about Long COVID and chronic fatigue syndrome

Scientists are looking into the similarities between Long Covid and chronic fatigue syndrome (CFS) – also known as myalgic encephalitis (ME). Here is what we know so far. 

  • 4 January 2023
  • 4 min read
  • by Priya Joi
Long COVID can cause fatigue. Credit: Shane on Unsplash
Long COVID can cause fatigue. Credit: Shane on Unsplash


1. Half of Long COVID patients have chronic fatigue syndrome

While fatigue has been linked to Long COVID right from the first few cases, Long COVID also presents with a constellation of symptoms including gastrointestinal issues, shortness of breath and loss of smell or taste.

In people who have had chronic fatigue syndrome (CFS), infection with SARS-CoV-2 could trigger viruses that have been dormant, leading to a resurgence of CFS symptoms.

To understand the prevalence of chronic fatigue in Long COVID patients, researchers in Iran undertook a meta-analysis covering 52 studies with 127,117 participants. They found that 42.5% of people who develop Long COVID have chronic fatigue that often persists for months. despite medical care.

2. Antivirals could help prevent Long COVID and treat CFS

People who took the antiviral drug nirmatrelvir shortly after becoming sick with COVID-19 were 26% less likely to develop Long COVID, according to a study published in November 2022 on a pre-print website. The study looked at people older than 60 years, and it's not clear yet whether the antiviral could be protective against Long COVID in younger people.

There has been anecdotal evidence of the use of this antiviral to treat Long COVID symptoms, and researchers suggest that antivirals could give people with ME/CFS enough of an immune boost to get relief from their symptoms, yet there have been no conclusive clinical trials yet.


3. COVID-19 could reactivate chronic fatigue symptoms

In people who have had chronic fatigue syndrome (CFS), infection with SARS-CoV-2 could trigger viruses that have been dormant, leading to a resurgence of CFS symptoms, according to a study published in December 2022. Herpes viruses such as Epstein-Barr virus (EBV) have been linked to triggering CFS.

The researchers found that antibody levels against several herpes viruses including EBV were raised in people who had CFS compared with in people who had never had CFS. This suggests that COVID-19 reactivated viruses linked to chronic fatigue symptoms.

4. Long COVID has reignited research into the causes of CFS

Long COVID has caused a resurgence of interest and study into CFS: a still mysterious condition that has had little attention from the research community for decades.

Beth Pollack, chronic disease researcher at MIT, describes CFS as a "neuroimmune, neuroinflammatory illness that affects numerous organ systems throughout the body, involving dysfunction of the vascular, autonomic, neurological, mitochondrial, metabolic, connective tissue, endocrine, and immune systems ".

An estimated 90% of people with CFS are never properly diagnosed, and many cases have been dismissed as a condition existing purely "in the mind " that can be treated with exercise therapy. In the US only about 15 doctors specialise in CFS.

5. There is controversy in treating Long COVID just as with CFS

There are no established treatments for Long COVID, just as there aren't for CFS. For decades, graded exercise therapy was advised for CFS, an approach that operated on the principle that steadily increasing the amount that people exercised would eventually return them to full health.

Others argued that this was a challenging treatment programme for people to follow when they often struggled to walk to the end of their road. However it is still now widely recommended as a treatment.

Long COVID has seen a division of opinions on the best approach to treatment, with some doctors continuing to emphasise the role of exercise in rehabilitation and others opposed to it. A better understanding of the underlying causes behind both CFS and Long COVID, as well as investment into clinical trials for treatment should help our understanding of both these conditions.

After trying to sign up participants for two years, the US National Institutes of Health's (NIH) RECOVER Long COVID initiative's two adult cohorts have finally met 50% of their enrolment targets for patients with acute COVID-19 infections, and 80% for post-acute infections, with an interim analysis expected early this year.