Inclusion criteria:

• In overall general good health.
• Females can enter and participate in this study if they are of non-childbearing potential (i.e., physiologically incapable of becoming pregnant) or if of childbearing potential, has a negative pregnancy test (urine) at screening and agrees to use GSK stipulated contraceptive methods.
• Must be newly diagnosed with a first recognized episode of GH at the time of the Screening Visit or within 3 months prior to the Screening Visit.

Exclusion criteria:

• Known or suspected to be immunocompromised (e.g., subjects receiving immunosuppressive therapy or chemotherapy for malignancy, or are seropositive for HIV).
• Received an investigational drug in the 30 days prior to the study.
• Receiving systemic antiviral or immunomodulatory treatments.
• Must not have received systemic antiviral treatments (e.g., valaciclovir, Famvir (famciclovir), acyclovir, lysine) within 3 days of starting study drug or immunomodulatory treatments in the 30 days before starting study drug.
• Clinically significant impaired renal function as defined by a creatinine clearance <30 ml/min, calculated using the Cockcroft-Gault formula.
• Clinically significant impaired hepatic function defined as an ALT (alanine transaminase) level > 5 times the normal upper limit.
• Subjects with active liver disease.
• Known to be hypersensitive to acyclovir, famciclovir, ganciclovir or any component of valaciclovir formulations.
• Known resistance to acyclovir, valaciclovir, penciclovir, famciclovir, ganciclovir or valganciclovir.
• Subjects with malabsorption or vomiting syndrome or other gastrointestinal dysfunction that might impair drug pharmacokinetics.
• Women contemplating pregnancy within the duration of the study drug dosing period.
• Women who are pregnant and/or nursing mothers
• Current history of alcohol or drug abuse.
• Received suppressive (daily) therapy for genital herpes prior to enrollment.