An estimated two million people in England and Scotland were experiencing symptoms of long COVID as of March 2024, according to the Office for National Statistics. Of these, 1.5 million said the condition was adversely affecting their day-to-day activities.
As more research emerges about long COVID, some experts are noticing that its trigger factors, symptoms, and causative mechanisms overlap with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
ME/CFS is characterized by severe fatigue that does not improve with rest, in addition to pain and cognitive problems. One in four patients are bed- or house-bound with severe forms of the condition, sometimes experiencing atypical seizures, and speech and swallowing difficulties.
Despite affecting around 250,000 people in the UK and around 2 million people in the European Union (EU), it is a relatively poorly funded disease research area. Increased research into long COVID is thus providing a much-needed boost to ME/CFS research.
“What we already know about the possible causation of ME/CFS is helping research into the causes of long COVID. At the same time, research into long COVID is opening up new avenues of research that may also be relevant to ME/CFS. It is becoming a two-way process,” Dr. Charles Shepherd, honorary medical adviser to the UK-based ME Association, told this news organization.
While funding remains an issue, promising research is currently underway in the UK to improve diagnosis, treatment, and understanding of the pathology of ME/CFS.
Viral Reactivation
Dr. David Newton is research director at ME Research UK. “Viral infection is commonly reported as a trigger for [ME/CFS, meaning that the disease] may be caused by reactivation of latent viruses, including human herpes viruses and enteroviruses,” he said.
Herpes viruses can lie dormant in their host’s immune system for long periods of time. They can be reactivated by factors including infections, stress, and a weakened immune system, and may cause temporary symptoms or persistent disease.
A 2021 pilot study found that people with ME/CFS have a higher concentration of human herpesvirus 6B (HHV-6B) DNA in their saliva, and that concentration correlates with symptom severity. HHV-6B is a common virus typically contracted during infancy and childhood.
A continuation of this research is now underway at Brunel University to improve understanding of HHV-6B’s role in the onset and progression of ME/CFS, and to support the development of diagnostic and prognostic markers, as well as therapeutics such as antiviral therapies.
Mitochondrial Dysfunction
Dr. Shepherd explained that there is now sound evidence demonstrating that biochemical abnormalities in ME/CFS affect how mitochondria produce energy after physical exertion. Research is thus underway to see if treating mitochondrial dysfunction improves ME/CFS symptoms.
A phase 2a placebo-controlled clinical trial from 2023 found that AXA1125, a drug that works by modulating energy metabolism, significantly improved symptoms of fatigue in patients with fatigue-dominant long COVID, although it did not improve mitochondrial respiration.
“[The findings suggest] that improving mitochondrial health may be one way to restore normal functioning among people with long COVID, and by extension CFS,” study author Betty Raman, associate professor of cardiovascular medicine at the University of Oxford, told this news organization. She noted, however, that plans for a phase III trial have stalled due to insufficient funding.