[Natural history of HIV infection in the child].

The evolution of HIV infection acquired by vertical transmission is more rapid in children than in adults. Mean survival ranges from 75 to 90 months and only 70% of children reach the age of 6. The natural history has two different patterns. Approximately 15-20% of the children develop severe immunodeficiency with opportunist infections and encephalopathy in the first year of life and die within the first three years. In the remaining 80-85%, the progression of the disease is slower and they live for several years. It has been postulated that the first group is constituted by cases of intrauterine transmission, whereas transmission is closer to birth in the second group. Aside from the moment of transmission, other factors--maternal, infant, and viral--influence the evolution of the disease. There is a direct relation between the severity of maternal disease and the risk that the child will acquire opportunist infections or die in the early years of life. The evolution of the disease also depends on clinical manifestations. The development of opportunist infections, encephalopathy, and delayed height and weight gain are associated with rapid progression, whereas lymphoid interstitial pneumonia and parotitis are associated with a slower progression. Viral load probably is the factor that best predicts the course of infection, although the load values associated with slow or rapid progression have not been clearly defined. However, it is evident that the lower the viral load, the lower the risk of infection. Although the viral load may be undetectable at birth, it rapidly reaches very high values, higher than in adults. Moreover, the state of equilibrium may take several years to attain. In any case, a linear relation cannot be established between viral load and the risk of progression, so other markers must be evaluated, such as CD4.