Mathematical formulation and studies of the risk parameters involved in HIV transmission.

The probability of becoming infected with HIV is formulated in terms of the total number of sexual contacts (N), the probability that a sexual act is infectious (r) and the prevalence (p). Using the appropriate equations we studied the effect of reducing each of the risk factors on lowering the probability of infection. We show that for many realistic situations the probability of becoming infected by multiple partners is equal to the probability of becoming infected by one partner in a monogamous relationship given that the prevalence is the same in both cases; however if the multiple partners are chosen over time from a pool of a growing prevalence, then one is better off in a monogamous relationship where that partner is chosen early in the epidemic.