A virus generally credited as the infectious agent of mononucleosis has so far eluded discovery. The term "infectious," often used in designating mononucleosis, seems to have been born of unfulfilled expectations.
Attempts to transmit the disease to laboratory animals by various inocula have proved unsuccessful. Human volunteers transfused with blood from patients with mononucleosis have, on a few occasions, developed suggestive clinical and laboratory evidence of the disease. It is noteworthy that the literature describes only a single case in which a patient accidentally acquired mononucleosis as a consequence of a blood transfusion from a donor with this disease. This statistic appears singularly unimpressive in view of the detection of mononucleosis in other young donors.
There are epidemiologic data acting as strong deterrents to the acceptance of the infectious nature of this disease. Why is it that a history of exposure, so common in patients with the viral exanthems, mumps