Indeed this has been discussed massively before. It was a big shock to me to discover that my own little theory that "I don't catch colds any more" was yet another very common ME/CFS phenomenon that I'd never heard about before finding Phoenix Rising.
When that old thread was active, there were actually two rival threads running: one was effectively "why do we always catch colds?" and the other was "why do we never catch colds?" It seemed at the time - and still does seem - a fundamentally important starting point for the definition of subsets. It's such a strong and clear phenomenon, although I can't imagine how you would demonstrate or prove it directly.
I wonder whether it correlates with acute viral onset, with those people being the ones who catch viruses all the time.
ETA: Actually I do have a wider theory which makes a lot of sense to me in this context. Whatever you are exposed to at the time of XMRV infection, is what you will be vulnerable to. If you get XMRV at the same time as a virus, you are vulnerable to viruses. If you get XMRV at the same time as you have mold exposure, you become vulnerable to mold. Whatever you have in your environment at the time of "the event" (which may or may not be the XMRV exposure), that is what your body is responding to at the time, and that becomes your personal "vulnerability profile". It vaguely seems to make sense that if XMRV is able to effect the B or T cell factories, the things that are activated at the time, then specifically which types of immune antibodies are active become those that are attacked, invaded, undermined and compromised. And of course, overall, you end up with a disease called ME/CFS that is so totally diverse that it doesn't appear like a consistent phenomenon.
My own "never catch colds" phenomenon has transformed somewhat in the past year or two. When some of my friends caught severe week-long flus during the swine flu epidemic, I had the only bad cold I've had in the last 10 years: it lasted about 2.5 days, which is 2 days longer than I've had previously had flu symptoms for. More recently, the effect seems to have sharpened. Now, I seem to experience short sharp flu symptoms whenever I meet up with friends. There's now one good friend of mine who seems to trigger a 12-hour flu whenever I see him - the last 4 times I've met up with him it's happened every time. Sore throat, shivers, headache, temperature...comes on within an hour of meeting up and is gone within 12 hours...I presume all that's "impossible" just like everything else....(sigh).
