The majority of children with HIV acquire the infection from their mothers, either during pregnancy, labour, and delivery or after birth during breastfeeding. Most infants become infected during the peripartum period or through ingestion of infected mother’s milk. Infected infants may have no symptoms or signs of infection soon after birth but usually develop features of infection in the early infancy period.
The natural history of perinatal HIV infection in infants is characterized by an early onset of symptoms, rapid disease progression, rapid CD4 lymphocyte loss and severe clinical course in 20% of the children. The HIV viral load (VL) is relatively higher in children than adults, probably because of the consequences of viral replication in the expanding lymphoid mass in infancy and the relatively immature immune system, which may make sustainable suppression of viral replication more difficult than in adults. In that connection, the prognosis of HIV infection in children is worse than in adults. In the absence of HAART, one third of children who acquire HIV through vertical transmission die in the first year, another one third die in second and third year, and the remaining one third survive for 3 to 15 years.