Inclusion Criteria:

- Age 15 years or older

- Within 14 days of initial symptoms of present illness diagnosed by a health care
provider as infectious mononucleosis and confirmed to be due to primary EBV by
antibody profile. The criteria for antibody confirmation of primary EBV at the
screening visit are: 1)Positive for anti-EBV VCA IgM antibody and negative for
anti-EBV EBNA1 IgG antibody; 2)EBV antibody testing will be done in the Clinical
Virology Research Laboratory using commercial ELISA kits (Diamedix Corporation,
Miami, FL).

- Willingness to sign the Informed Consent Form (ICF)

- Willingness to contribute samples of blood and oral washings at regular intervals

- Males and females must use effective contraception during treatment and for at least
90 days following treatment

- Negative pregnancy test result at the Screening Visit for females of childbearing
potential (including females who have had a bilateral tubal ligation). Female
patients of childbearing potential must be willing to use an approved method of
double-barrier contraception (hormonal plus barrier or barrier plus barrier, eg,
diaphragm plus condom) from the time of first dose administration until 90 days after
completion of dosing and male patients with female partners of childbearing potential
must be willing to use a condom. Patients who are sterile or infertile (defined as
those who are postmenopausal or have undergone a complete hysterectomy) are eligible.

- Estimated creatinine clearance (Cockcroft and Gault method) ≥ 60 ml/min

- Absolute neutrophil count ≥ 1000 cells/microliter

- Platelets ≥ 100,000/microliter

- Hemoglobin ≥ 9.5 g/dL

Exclusion Criteria:

- Previous history of infectious mononucleosis-like illness

- Immunosuppressed due to medical disease and/or immunosuppressive or immunomodulating
medications (e.g., corticosteroids prior to enrollment, cytotoxic drugs, interferons)

- Another intercurrent viral infection (including HIV), based on history or referring
physician medical evaluation

- More than 7 days elapsed since onset of illness (including screening time)

- The following concomitant medications are prohibited: probenecid, trimethoprim,
myelosuppressive therapies, and medications known to be nephrotoxic

- Breast feeding during the study

- Corticosteroids are not permitted. If they are prescribed by the subject's primary
physician for treatment of this acute disease after the subject has enrolled, the
subject will be replaced.