PIP: Virtually all pediatric acquired immunodeficiency syndrome (AIDS) cases result from either vertical infection (transmission from mother to child before or at birth) or infection through transfusion with blood products that contain the human immunodeficiency virus (HIV). The risk of passing HIV infection on to an unborn child is about 25-30% if the mother is essentially healthy and higher if the mother is already showing signs of AIDS. Since maternal antibodies can persist in the infant's blood for as long as 15 months after birth, it is difficult to tell whether a positive HIV test result in an infant under this age is valid. The clinical case definition of pediatric AIDS requires the presence of 2 major signs (weight loss or abnormally slow growth, chronic diarrhea for more than 1 months, or prolonged or intermittent fever for more than 1 month) and 2 minor signs (generalized lymph node enlargement, oropharyngeal candidiasis, recurrent infections, generalized dementia, persistent cough for more than 1 month, or confirmed infection with HIV in the mother). However, diagnosis is complicated by the fact that signs and symptoms associated with HIV infection are similar to those of other treatable diseases common among children in developing countries (e.g., malnutrition, tuberculosis, and chronic diarrhea). Mothers are advised to continue breastfeeding, even where HIV indication is indicated, since there is no evidence that nursing is a significant route of infection. In addition, there is no evidence that immunizations given by trained health workers using sterile equipment transmit HIV infection.