However, the exertion had to be a lot more when I was mildly affected. If you don't have an abnormal response to exertion, I'm not sure you have this condition.
If I had a photo of someone, and I was trying to explain to my friend whether or not the person was attractive, I wouldn't just say "her eyes are between 3.1 and 3.3 inches apart" - I would just show my friend the photo and let him decide.
I am not saying it can't be the case that those with strong strong PEM suffer from their own unique illness, I'm just saying that until we find the cause, there's no point in assuming that. If you codify, you capture everyone, it doesn't exclude people who believe abnormal response to exertion as their defining characteristic. Why not win both ways?
People with chronic infections can be picked up by other researchers.