Myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis​/​chronic fatigue syndrome (ME/CFS) is a disablingchronic illness. People with ME/CFS experience profound fatigue that does not go away with rest, as well as problems with sleep and memory or concentration. The hallmark symptom is post-exertional malaise (PEM), a worsening of the illness that can start immediately or up to days after even minor physical or mental activity. This "crash" can last hours, days or several months. Further common symptoms include orthostatic intolerance—dizziness or faintness when upright—and pain.

The cause of the disease is unknown. ME/CFS often starts after an infection, such as infectious mononucleosis, and the illness has a genetic risk factor that can also run in families. Studies find impairment in the nervous and immune systems, as well as in energy production. A diagnosis is established with the presence of clinical symptoms and systematic differential diagnosis, as there is no verified diagnostic laboratory test or imaging procedure available.

ME/CFS symptoms can improve or worsen over time, but a full recovery is uncommon. No therapies or medications are approved to treat the cause of the condition, and treatment or management is aimed at relieving symptoms. Pacing of activities can help avoid PEM which can worsen symptoms for extended periods, and counselling may help in coping with the illness. Before the COVID-19 pandemic, ME/CFS affected two to nine out of every 1,000 people, depending on the diagnostic criteria. Since the pandemic began, with the similarity of long COVID, many more people fit a diagnosis of ME/CFS. It occurs more often in women than in men and is more common in middle age, but can occur at all ages, including childhood.

The societal and economic impact of the disease is large, and the symptoms can be socially isolating. About a quarter of those affected are unable to leave their bed or home. People with ME/CFS often face stigma in healthcare settings, and care is complicated by controversies around the cause and treatments of the illness. Doctors may be unfamiliar with diagnosing the illness, as it is often not fully covered in medical school. Historically, research funding for ME/CFS has been far below that of diseases with comparable impact.