The Available Pool of Sex Partners and Risk for a Current Sexually Transmitted Infection

Sexually transmitted infection (STI) transmission models propose that incident STIs are related to exposure to infected sex partners. The objective of this study was to determine whether the prevalence of STIs among the available pool of sex partners in a neighborhood, measured indirectly, is an independent determinant of a current incident STI.The target population comprised 58,299 English-speaking, sexually active 15- to 24-year-olds in 486 census block groups (CBGs) in Baltimore, MD. A sample of 65 CBGs was selected using a stratified, systematic, probability-proportional-to-size strategy and 13,873 households were randomly selected. From 2004 through 2007, research assistants administered an audio computer-assisted interview survey and collected biologic samples for gonorrhea and chlamydia testing.The final sample size included 575 participants from 63 CBGs. Additional data provided gonorrhea prevalence from 2004 through 2005 per 15- to 49-year-old persons per 100,000 per CBG. After adjustment for individual-level STI risk factors in a multilevel probability model, adolescents and young adults living in high (vs. low) prevalence STI areas were 4.73 times (95% confidence interval [CI]: 3.65-6.15) more likely to have a current incident STI.To inform prevention programs, future research should focus on identifying mechanisms through which context causes changes in local sexual networks and their STI prevalence.