My friend has chronic fatigue syndrome.  Its sad
I can understand tha this is devastating because it limits your ability to perform everyday functions.
Yes.  He has a lot of trouble doing even everyday things in life
It can be biological or infections or genetic. Tests must be performed to find out the cause.
I did not know it had so many causes
The ultimate diagnosis is based on a person's symptoms.
That is interesting.  Can they just treat an infection for it?
There is no sure that is approved in the US as of now. It would take just a lifestyle change I think.