You been able to get hold of the full paper? I don't know how they can conclude that a second infection of HHV-6 might be the trigger and have led to the experienced symptoms. I don't clearly know enough about virology. Presumably from the patients point of view there was a specific event that led to the production of their symptoms i.e. a starting point. I don't know how you might conclude that an 'unrelated strain' of infection currently in the body, entered the body at a certain time that coincides with the onset of symptoms. Maybe you don't. But if we are saying HHV-6 is asymptomatic how would the patient know or anyone else whether it was a trigger or not? Anyway... perhaps the full paper can help explain.