If an athlete becomes housebound - a subtle change can't cause this. But we can't find what is it - which is a problem. In 1985 scientists said that EBV being the cause of ME was absurd. They didn't believe that it could cause this degree of disability. Coxsackie and enteroviruses aren't dramatic results from biopsies so are unlikely candidates.
Symptoms are volume dependent.
This pattern was what was thought to be the process, but isn't correct. Feel faint but recover. ME, however, has low blood volume and blood trapping in legs. They're working on a test. Patient lies down and take BP and pulse for 10 minutes.