Epidemiology Humans are the only source of infection for this highly contagious virus. In-utero infection can also occur. Introduction of a varicella-zoster virus infection into a household usually results in infection of nearly all susceptible persons. Nosocomial transmission is well documented in pediatric units, but transmission is extremely rare in newborn nurseries. Most reported cases of chickenpox occur in children younger than 10 years of age, but varicella in adolescents and young adults may be becoming more common.
Immunity is generally lifelong.
Symptomatic reinfection is rare in healthy persons, although aymptomatic reinfection do occur. Varicella is most common during the late winter and early spring. Aymptomatic primary infection is unusual. Other group of pediatric patients who may experience unusally severe disease or a higher rate of complications include children in the first year of life, adolescents, pregnant adolescents, and patients receiving systemic steroids. Congenital varicella can also occur if infection of the mother occurs early in pregnancy.