It may be that most people who get CFS have been carrying latent XMRV around for a long time. Some of those people may get "gradual onset" as the result of numerous low-level co-infections, while others get "sudden onset" following an acute infection with some more virulent “trigger” such as with EBV or a flu virus. It also may be that, in some people, the acute triggering infection is XMRV itself.
According to Dr. Mikovits, XMRV replicates when infected cells divide and “only when they divide.” There is rapid cell division in an activated immune system, so that may be a key pathway to activating XMRV. That would also suggest an explanation as to how people become ill after things like vaccinations or even after severe physical trauma, such as in an auto accident.
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I had “sudden onset” three weeks after the most intense “flu” of my life. During those three intermediate weeks, I felt I was recovering normally – although, I was occasionally tired and my vision occasionally seemed a bit “off,” as though my visual perspective was slightly distorted.
On April 15, 1983 (at around 5:00 PM, to be exact), I became extremely dizzy out of the blue. That is what I have always considered the “sudden onset” of my symptoms. I developed a bunch of other classic CFS symptoms in the days, weeks and months that followed. In retrospect, the flu I experienced three weeks earlier seems to have been a clear precursor.
I was unsure of whether this kind of onset was consistent with CFS until I read a short 1986 monograph by Dr. Melvin Ramsay entitled “MYALGIC ENCEPHALOMYELITIS: A Baffling Syndrome With a Tragic Aftermath.” In it he writes:
I had sudden onset, but I'm sure that other more gradual onset types occur.