DEFINING THE TIME OF FETAL OR PERINATAL ACQUISITION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION ON THE BASIS OF AGE AT FIRST POSITIVE CULTURE

It has been suggested that a positive diagnostic test for human immuno deficiency virus type 1 (HIV-1) during the first 48 h of life is indic ative of intrauterine transmission, whereas negative tests during the first week with positive tests later indicate intrapartum transmission . On the basis of data from all 140 infected infants in the Women and Infants Transmission Study (WITS), the probability was estimated that an HIV-1 culture would be positive for the first time at each day of l ife if cultures were performed daily. The estimated probabilities (+/- SE) by days 0, 2, 4, 7, 9, 16, and 30 of life are 27.4% (+/-6.4%), 27. 4% (+/-13.0%), 45.3% (+/-20.5%), 45.3% (+/-22.5%), 65.3% (+/-20.0%), 8 8.4% (+/-7.8%), and 89.3% (+/-7.0%), respectively. The initial 27% pro bability is consistent with the hypothesis that transmission usually o ccurs during the intrapartum period. However, the distribution of age at first positive culture does not separate clearly into two distinct intervals. More definitive methods for determining the timing of trans mission are needed.