Trends in chlamydia prevalence in the United States, 2005-2016.

In the United States (US), chlamydia is the most frequently reported sexually transmitted infection that is nationally notifiable. We examined trends in chlamydia prevalence in the US in 2011-2016 compared with 2005-2010. Cross-sectional, nationally representative surveys, National Health and Nutrition Examination Surveys (NHANES), were used to compare national chlamydia prevalence estimates from 2011 to 2016 with those from 2005 to 2010, and changes in prevalence since 1999-2004 were also reviewed. Persons aged 18-39 years were included in these analyses. Prevalence of chlamydia was based on results from urine specimens. Results were weighted to represent the U.S. civilian, noninstitutionalized population. The baseline characteristics of the study population were similar in gender, age and race/ethnicity between the two groups (P > 0.05). The overall chlamydia prevalence was 1.88% (95% confidence interval [CI] 1.55-2.22%) in 2011-2016 and 1.57% (95% CI 1.27-1.87%) in 2005-2010, a relative increase of 19.7% (95% CI 0.2-39.2%; P < 0.05) between the two surveys. Increases in chlamydia prevalence was especially concentrated in persons who were male, aged 18 to 29 years, had > high school educational level, never married, age at first sex < 18 years, had 2-5 sexual partners in lifetime and had no past sexually transmitted diagnosis between 2005 and 2016 (P < 0.05). Multivariable logistic regression analysis demonstrated that chlamydia was more prevalent in those aged 18-29 years, being non-Hispanic Blacks, had high school educational level, being widowed/divorced/separated and had > 5 sexual partners. The chlamydia prevalence had an increasing trend from 2005-2010 to 2011-2016. Those with high chlamydia prevalence such as sexually active young adults and Non-Hispanic Black should be screened annually so that infected persons can be diagnosed and they and their sex partners can be treated promptly.