Okay, I want to start out by saying my intention is NOT for this thread to be about Hyde-bashing. I have great respect for the man, who has done so much to redefine this illlness, and even written his compassion into that definition in a beautiful way. My question is about this quote I read of his, date unknown, accuracy of quote unknown, regarding XMRV: 'In four of the sixty M.E. epidemics an enterovirus was recovered. In over 50 other [M.E.] epidemics, no virus was recovered but the average incubation period of the infection in these epidemics was 3-6 days, as it is in all enterovirus infections. However, the "incubation period of [the not enterovirus, but retrovirus] XMRV is up to 21 days which makes it impossible to cause an epidemic illness.' The question in particular that arises for me, (besides whence came the 21-day incubation,) is that if one group of people were all exposed at around the same time, and the incubation period is consistent (whatever that period is) how does that preclude epidemic outbreaks? As far as I can tell that would mean all susceptible people, that is to say people with whatever immune terrain and cofactors necessary to encourage the retrovirus to incubate, would all come down with it at approximately the same time, 21 days or what have you later---would they not? How is a six-day incubation an epidemic when a 21-day one is not? Logically it seems it is still an epidemic, it just shows up in the population after a longer delay. I have no attachment one way or another what factor this retrovirus plays in our illness. Clearly it has a role. I am just curious about the logic here. I am not knowledgeable in this area. From Merriam Webster, defining it as an adjective: 1epidemic adj \ˌe-pə-ˈde-mik\ Definition of EPIDEMIC 1 : affecting or tending to affect a disproportionately large number of individuals within a population, community, or region at the same time <typhoid was epidemic> As a noun: : an outbreak or product of sudden rapid spread, growth, or development <an epidemic of bankruptcies> Perhaps in medical world, something is only considered an epidemic when it is rapid? Is there a term for outbreaks in disproportionately large number of individuals within a population, community, or region at the same time after a longer delay? Typhoid, by the way, (the example used by M-W to define epidemic) has an incubation period of ten to twenty days according to one source.