• Change in best ear hearing assessments. [ Time Frame: Between baseline and 6 months. ] [ Designated as safety issue: No ]
  

• Neurological assessments-utilizing the Bayley Scales of Infant and Toddler Development. [ Time Frame: 12 and 24 months of life ] [ Designated as safety issue: No ]
  
• Overall profile of adverse events thought to be related to the study therapy. [ Time Frame: Through study month 7 ] [ Designated as safety issue: Yes ]
  
• Age-appropriate audiological assessments. [ Time Frame: Assessed at baseline, 6, 12, and 24 months. ] [ Designated as safety issue: No ]
  
• Correlation of change in whole blood viral load with audiologic and neurodevelopmental outcomes. [ Time Frame: Blood will be drawn at each study visit from Day 1 through Month 7. ] [ Designated as safety issue: No ]
  
• Adverse events which lead to permanent discontinuation of valganciclovir therapy or to irreversible outcome of the adverse event. [ Time Frame: Through study month 7 ] [ Designated as safety issue: Yes ]
  

This study is a multi-center, prospective, international, phase III, randomized and blinded investigation of 6 weeks versus 6 months of oral valganciclovir therapy in babies with symptomatic congenital cytomegalovirus (CMV) disease. Following enrollment, study subjects will receive 6 weeks of oral valganciclovir. Near the end of the 6-week course, subjects will be randomized in a 1:1 fashion either to continue on valganciclovir to complete 6 months of therapy or to begin a matching placebo to complete the 6 months. Study subjects will be stratified according to whether or not there is central nervous system (CNS) involvement at study entry. The total number of enrolled subjects will be 94. During the 6-month treatment period and the 1 month thereafter, study subjects will be followed weekly for 4 weeks, then every other week for 8 weeks, then every month for 4 months. At each of these visits, safety labs will be checked, growth parameters recorded, and adverse events assessed. The dose of study medication will be adjusted for weight gain at each of these study visits. Whole blood will be obtained for CMV viral load at each of these visits as well. Hearing outcomes will be assessed at baseline, 6 months, 12 months, and 24 months. Developmental outcomes will be assessed at 12 months, and 24 months. Changes in whole blood viral load measurements will be correlated with both hearing and neurologic outcomes. In study subjects with increasing whole blood viral loads during the course of treatment, assessment for antiviral resistance may be undertaken. Safety assessments include hematology labs, chemistry labs, physical examinations, and adverse event data performed/collected serially. Development of neutropenia will be confirmed by repeat blood testing within one week, and study drug will be held until it resolves. Efficacy assessments will include hearing assessments at baseline, 6 months, 12 months, and 24 months; and neurodevelopmental assessments at 12 months and 24 months. Study objectives are: to compare the impact on hearing outcomes of 6 weeks versus 6 months of antiviral treatment with valganciclovir oral solution in infants with symptomatic congenital CMV disease; to compare the safety profile of 6 weeks versus 6 months of antiviral therapy with valganciclovir oral solution in infants with symptomatic congenital CMV disease; to compare the impact on neurologic outcomes of 6 weeks versus 6 months of antiviral treatment with valganciclovir oral solution in infants with symptomatic congenital CMV disease; and to correlate change in whole blood viral load with hearing and neurologic outcomes. The primary study endpoint is change in best ear hearing assessments between baseline and 6 months. Secondary study endpoints are: adverse events which lead to permanent discontinuation of valganciclovir therapy or to irreversible outcome of the adverse event; change in best ear hearing assessments between baseline and 12 months; change in best ear hearing assessments between baseline and 24 months; maximum change in hearing assessments between baseline and 6, 12, and 24 months over left and right ears; hearing deterioration between baseline and 6, 12, or 24 months over left and right ears; neurologic impairment at 12 months of life, utilizing the Bayley Scales of Infant and Toddler Development (BSITD); and neurologic impairment at 24 months of life, utilizing the BSITD. Tertiary study endpoints are overall profile of adverse events thought to be related to the study therapy; correlation of change in whole blood viral load with change in hearing between baseline and 12 months of age over left and right ears; correlation of change in whole blood viral load with neurologic impairment at 12 months of life, utilizing the BSITD; and characterization of the population pharmacokinetics of valganciclovir and assessment of adherence during treatment.