Maybe I'm not getting it, but wouldn't CFS patients, by definition, have had to have been "infected" (if that's what happened), and have developed symptoms, for at least 6 months to even get a diagnosis of CFS?
Are you confusing "infection" with "culturing" the virus for purposes of testing? I don't think the abstract mentioned anything about culturing the blood. (I realize my terminology is probably off. I have trouble following all this.) Just looks to me like you're comparing two different things.