one of the studies that first made me question the concept of viral "infectiousness" was this 2005 paper. it is assumed that EBV reactivates when the human is stressed, but these are astronauts that test negative for symptoms.

They are asymptomatic yet under none physiologic conditions in space produce fragments which we call epstein barr virus.

It dawned on me when reading this paper that it could be reactivation of a virus incorporated into our molecular biology or it could be that humans create the dna in times of stress and shed these particles as a purge of internal derangements.