All questions about ME/CFS and long COVID
What causes ME/CFS?
The cause is unknown. It often develops after an infection, and it's still being investigated.
The full answer, with the sources, is in the guide.
Sources
- NHS: Myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS), overview
- ME Association: What are ME/CFS and long COVID? (summarises the NICE 2021 guideline)
Reviewed 2026-11-09 · next review 2027-11-09