Incidence and Prevalence of Trichomonas vaginalis infection among persons aged 15-59: United States, 2018.

BACKGROUND: Trichomonas vaginalis (TV) is a sexually transmitted parasite associated with multiple adverse outcomes in women. Estimating TV incidence is challenging due to its largely asymptomatic presentation.

METHODS: Per capita prevalence was estimated using the National Health and Nutrition Examination Survey, 2013-2018. Incidence was estimated using ordinary differential equations assuming static incidence at steady state and fit using Bayesian techniques. Model inputs included estimates of: proportion of asymptomatic cases, natural clearance, and time to symptomatic treatment seeking. Posterior distributions were drawn, and uncertainty reported, from 25th (Q1) to 75th (Q3) percentiles. Aggregated measures were estimated by combining component distributions.

RESULTS: Among 15-59 year-olds in 2018, the number of prevalent TV infections was 2.5 (Q1=2.4, Q3=2.7) million overall, 435,000 (Q1=382,000, Q3=492,000) among men, and 2.1 (Q1=2.0, Q3=2.2) million among women; the number of incident infections was 7.4 (Q1=6.6, Q3=8.3) million, 4.1 (Q1=3.5, Q3=4.9) million, and 3.2 (Q1=2.7, Q3=3.7) million among all persons, men, and women, respectively. Persons aged 15-24 years comprised 15.7% and 17.6% of all prevalent and incident infections, respectively; prevalence and incidence in both sexes increased with age. Incidence in both sexes were highly dependent upon estimates of natural clearance, which were based on little data.

CONCLUSIONS: Prevalence and incidence of TV are substantial in the United States, particularly among those aged ≥25 years. Though estimated prevalence is higher in women, estimated incidence is higher in men. Data on key parameters of TV infection are limited; future research should focus on clarifying the natural history of TV.