Condom use by female sex workers and their clients in Mexico: who decides and does it matter?

OBJECTIVES: To explore the effect of different patterns of condom use by clients and female sex workers (FSW) on HIV transmission in Mexico. METHODS: Data from 2401 face-to-face interviews among FSW from Morelos and Michoacán in Mexico were used to build and parameterise a deterministic model of HIV transmission between FSW, their stable partners and clients. RESULTS: For the observed patterns of condom use among FSW, a range of patterns of use among clients would be consistent. Two extreme patterns were explored: either clients conformed to FSW decision, or they had a strict preference for bought sex with or without condoms. HIV prevalence in the model is greater in the first of these scenarios. CONCLUSIONS: Patterns of condom use between sex workers and clients are an important, but hidden, determinant of epidemic spread. More detailed information on condom use negotiation and behavioural patterns of clients is needed to understand the potential for transmission in these populations and in order to direct intervention efforts more effectively.