Limits on Oral Transmission of HIV-1 [Cohen MS, et al. Lancet 2000; 356: 272]: This is a commentary from Myron Cohen and colleagues concerning oral transmission of HIV. Three potential vehicles are discussed: saliva, semen and breast milk. Salivary secretions appear to be very low-risk due to low levels of HIV in saliva and inhibitory components found in salivary secretions [J Dent Assoc 1998; 129: 851]. In addition, the evidence of transmission from saliva seems to be very rare [AIDS 1998; 12: 2095]. By contrast, some studies show that up to 16.2% of cases of vertical transmission can be ascribed to breastfeeding [JAMA 2000; 283: 1167]. This may be explained by the high loads of HIV in breast milk, the low gastric acidity in neonates that may facilitate transmission, and the isotonic secretions of breast milk that may inhibit the components of saliva that inhibit HIV [JID 1999; 180: 93]. The risk with oral exposure to semen is controversial. Rothenberg [AIDS 1998; 12: 2095] summarized 21 case reports, but concluded that oral exposure could be identified as an independent risk factor in only three. Recent studies of primary infection have identified oral sex as the mechanism of HIV infection in 6.6% of 122 patients [Dillon B, et al. CROI 2000, abstract 473], and another report indicates this mechanism in four of 46 newly infected men [Ann Intern Med 1996; 125: 257]. The author concluded the following: 1. that saliva exposure represents an "exceedingly-small" risk; 2. breastfeeding is a substantial risk; and 3. receptive fellatio is an inefficient mechanism of transmission, but cannot be considered safe sex. posted 8/7/2000