I run low-grade fevers most of the time. If ever I'm well enough to exercise, and I sometimes do (damn the consequences!), I usually come down with a fever within a couple of days and am completely immobilized (essentially looks just like the flu).
My normal temp seems to be about 100.5, but at times when I've been afebrile, it's lower than 98.
I tested negative for blood cultures/systemic bacterial infection, and my doctor quickly dismissed the fever. My TCM practitioner addresses the fever as a deficiency illness, though I'm not sure exactly what that means in Western terms. He treats it by giving me tonifying herbs, which can't be given during a pathogen (virus, bacteria, etc.), and often this brings the fever down. Obviously, my herbs switch from tonifying to clearing depending on symptoms. So, I do believe it's possible to weakened rather than diseased, if that makes sense...? I am likely to get every upper respiratory infection around and think it might be systemic (mycoplasma?), but I don't know if that's also a sign of overall weakness. I always sort of figure that when I get the PEM, I'm super drained and with that comes a deficiency fever. I hope this helps!
I'm curious about how "normal" fever is with CFS in general.