"Do you think your main partner has other sex partners?" A simple question provides insight into sexual risk in Jamaica.

To estimate the association between a simple measure of sexual partner concurrency and sexually transmitted infection (STI) we conducted a cross-sectional population-based household survey (n = 1795) and targeted surveys of people at venues where people meet sexual partners (n = 1580) to ask about sexual behaviour. Persons interviewed at venues were tested for HIV, gonorrhoea, chlamydia, and trichomoniasis. We compared the association between STI and reporting a partner had other partners.