Prevalence of Chlamydia Trachomatis — United States, 2007–2010

Background: Chlamydia is the most commonly reported infection in the United States with over 1.4 million cases reported in 2011. As chlamydia is usually asymptomatic and can lead to adverse reproductive outcomes, routine screening is recommended for sexually-active young women. However, it is likely that many infections are not identified and case reports underestimate true morbidity. 

Methods: We estimated prevalence of chlamydial infection by sex, age, race, and self-reported sexual activity (measured through audio computer-assisted self-interview) with corresponding 95% confidence intervals (CI) using data from the most current National Health and Nutrition Examination Surveys (2007-2010); data from the 2011–2012 survey will be added if available before the conference. Estimates were weighted to be nationally representative and to account for oversampling and nonresponse. We estimated the number of infections in the population by multiplying census estimates by weighted prevalence estimates.

Results: Among the 5,610 participants aged 14–39 years tested for chlamydial infection, 1.7% (95% CI: 1.3%, 2.0%) were infected, suggesting that there are 1.8 million prevalent infections nationally (range:  1.4–2.1 million). Among the 48% of female adolescents (aged 14–19 years) who reported being sexually-active, prevalence was 7.7% (95% CI: 4.7%, 10.8%). Prevalence among sexually-active, non-Hispanic black female adolescents (17.5% (95% CI: 11.0%, 24.0%)) was higher than prevalence among sexually-active, non-Hispanic white female adolescents (4.9% (95% CI: 0.4%, 9.4%)).

Conclusions: Based on findings from a nationally-representative survey, we document a large burden of prevalent chlamydial infections suggesting that many infections are not diagnosed and reported. High prevalence among sexually-active young women suggests that routine screening is warranted and substantial racial disparities highlight the need for targeted interventions.