yes, I rarely get a cold or a flu; if I do, it's generally milder and is shorter in duration to when my kids get sick. I have taken care of both kids with fevers and lots of coughing/sneezing and not gotten anything from them. If my throat and ears start feeling "itchy" this is usually a sign for me of a virus trying to take hold, so I dose myself with echinachea/goldenseal for a couple of days and then I'm fine.
one theory I heard was that some people who have been exposed to viruses like mono, epstein barr, herpes, etc. somehow it screws up their immune system and the immune system forgets to turn itself down, it's always in "attack" mode and starts attacking everything in sight, from harmless bits of dust to everyday chemicals. when this happens, histamine is released into the system, causing inflammation. if you're exposed to a virus such as cold or flu, your body is already "on alert" so to speak, so you are less likely to get sick. since the whole body is over-wired, the histamine reactions can take place anywhere in the body, not just the typical sinuses/throat/lungs but digestive system, nervous system,etc. accounting for systemic reactions. another theory I heard was that this tendency to go into immune system hyperdrive when exposed to these viruses is genetic in origin, passed on in families, therefore the tendency for children of parents with MCS/CFIDS to develop it also.