PEDIATRIC HIV UPDATE

Less than half of the paediatric HIV infections recorded in Australia have resulted from perinatal transmission, but in recent years this ha s been the predominant mode of infection. There are 136 infants who ar e known to have been exposed perinatally to HIV in Australia: 49 of th ese are infected. Caesarean section is thought now not to reduce the r isk of perinatal transmission (PNT); rather, the risk increases with d uration of membrane rupture and rises rapidly after 4 h of membrane ru pture. However, no data exist to show that interventions to expediate delivery after membrane rupture reduce the risk of PNT. Data such as t hese suggest that the majority of perinatal infections (probably about 60%) occur close to the time of delivery. While the overall risk of P NT for non-breast fed infants is approximately 20-25%, the risk of inf ection for the infant is considerably increased when there is evidence of increased maternal viral burden. Advanced maternal disease predict s that if the infant is infected there is more likely to be early prog ression of HIV than is the case for the less frequently infected infan ts of mothers who are asymptomatic. Bottle feeding may prevent infecti on of 10% of children exposed perinatally. Use of zidovudine by the mo ther in the third trimester and i.v. zidovudine during labour, followe d by oral zidovudine for the infant for 6 weeks can reduce the PNT rat e by two thirds, to about 8%. Approximately 3% of uninfected infants w ith perinatal HIV exposure may be found to be transiently virus positi ve but eventually become antibody negative and thus appear to have eli minated the virus. The risk of Pneumocystis carinii pneumonitis (PCP) cannot be predicted on the basis of CD4 count and it is recommended th at all children of infected mothers commence PCP prophylaxis around th e age of 6 weeks-2 months and continue that therapy until the age of 1 2 months or until it becomes clear that the infant is uninfected. The cumulative risk of AIDS increases rapidly during the first year of lif e to about 20%, then more slowly at a rate of about 2 or 3% a year. Th e shape of this curve reveals the bimodal progression of HIV disease i n children. About 15-20% of children rapidly develop a severe immune d eficiency, opportunistic infections and, in most cases, encephalopathy . There is a very high morbidity rate in this group of children, most of whom die before the age of 3 or 4 years. In contrast, 80-85% of chi ldren only become immunodeficient after a relatively long period, whic h is similar to or perhaps even longer than that in adults. Recent stu dies indicate that zidovudine antiviral monotherapy is no longer appro priate. While no clear alternative to monotherapy has emerged most wou ld, wherever possible, commence antiretroviral therapy with a combinat ion of two or three drugs including zidovudine plus didanosine or lami vudine. If a third drug is used it would probably be a protease inhibi tor.