Overview and Terminology

ME/CFS has been recognized as a distinct clinical entity by major health organizations, including the World Health Organization (ICD-11 code 8E49), the Centers for Disease Control and Prevention, and the National Institutes of Health. The condition affects an estimated 0.89% to 2.5% of the global population, with significant variation based on diagnostic criteria used.

The terminology surrounding this condition has evolved over time. While “chronic fatigue syndrome” became widely used in the late 1980s, many patient advocates and researchers prefer “myalgic encephalomyelitis” as it better reflects the neurological and immunological aspects of the disease. This document uses the combined term ME/CFS to acknowledge both naming conventions.