Transmission of viral infection from person to person is difficult to observe in great detail, particularly in children. Through studies focused on herpesvirus infections (herpes simplex virus-1, Epstein-Barr virus, cytomegalovirus, human herpesvirus 6, and human herpesvirus 8) in a cohort of Ugandan infants, mothers and siblings, we have begun to quantify and model transmission of these viruses. We are using statistical and mathematical models to compare patterns of viral shedding between infants, siblings and mothers. These analyses provide a unique window into the maturation of the immune response against each of these viral pathogens with age. We are also using models to identify fundamental and virus-specific features of viral transmission, including viral load necessary for transmission, risk factors for transmission, viral incubation period, and infectivity of siblings versus mothers for each virus.