Sexually Transmitted Infections*
About
Number of newly diagnosed chlamydia cases per 100,000 population. The 2025 Annual Data Release used data from 2022 for this measure.
Chlamydia incidence rates are associated with unsafe sexual activity. Chlamydia is the most common bacterial sexually transmitted infection (STI) in North America and is one of the major causes of tubal infertility, ectopic pregnancy, pelvic inflammatory disease, and chronic pelvic pain.1 Every year, around three million teenagers contract an STD, with females aged 15 to 19 facing the highest risk compared to other age and gender groups. STIs are associated with a significantly increased risk of morbidity and mortality, including increased risk of cervical cancer, infertility, and premature death.2 STIs also have a high economic burden on society. This measure is also significant to health equity as chlamydia disproportionally affects underserved communities, particularly minoritized adolescent women.3
Data and methods
Data Source
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Data on sexually transmitted infections were provided by the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP). The NCHHSTP is responsible for public health surveillance, prevention research, and programs to prevent and control human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS), other sexually transmitted diseases (STDs), viral hepatitis, and tuberculosis (TB). Center staff work in collaboration with governmental and nongovernmental partners at community, state, national, and international levels, applying well-integrated multidisciplinary programs of research, surveillance, technical assistance, and evaluation.
Website to download data
For more detailed methodological information
Key Measure Methods
Sexually Transmitted Infections is a rate
Sexually Transmitted Infections is the number of newly diagnosed chlamydia cases per 100,000 population in a county. Rates measure the number of events in a given time period divided by the average number of people at risk during that period. Rates help us compare risks of health factors across counties with different population sizes.
Some data are suppressed
A missing value is reported for counties with 1 to 3 cases in the time frame.
Caution should be used when comparing these estimates across states
Chlamydia screening patterns may vary between states and health care systems. Differences in rates may reflect these different screening practices, rather than differences in the underlying rates of disease. Additionally, states report STI data to The Centers for Disease Control and Prevention (CDC) using a mix of electronic reporting systems.
Caution should be used when comparing these estimates across years
The impact of the pandemic likely led to reduced screening and delayed reporting of chlamydia cases and data from the 2023 and 2024 Annual Data Releases should be interpreted with caution for this reason.
Measure limitations
Increases in reported infections may reflect true increases in disease, but may also reflect expanded screening, use of increasingly sensitive diagnostic tests, increased emphasis on case reporting from providers and laboratories, and improvement in the information systems for reporting. Communities with lower rates of screening may report artificially low rates of chlamydia incidence. Finally, chlamydia is only one of many STIs.
Numerator
The numerator is the number of reported chlamydia cases in a county.
Denominator
The denominator is the total county population.
Can This Measure Be Used to Track Progress
This measure can be used to measure progress with some caveats. While an increase in reported infections may reflect an increase in disease incidence, the increase could also be due to other factors. For example, an increase may also be reflective of expanded screening, better diagnostic tests, or improved reporting by a clinic or local health department. Communities with poor screening rates may have artificially low rates of sexually transmitted diseases.
Finding More Data
Disaggregation means breaking data down into smaller, meaningful subgroups. Disaggregated data are often broken down by characteristics of people or where they live. Disaggregated data can reveal inequalities that are otherwise hidden. These data can be disaggregated by:
- Age
- Gender
- Race
While there is no national source for stratifying STI rates, most states publish STI data, often with age, race, or gender breakdowns.
References
- Genuis SJ, Genuis SK. Managing the sexually transmitted disease pandemic: A time for reevaluation. American Journal of Obstetrics & Gynecology. 2004;191:1103-1112.
- Meade CS, Ickovics JR. Systematic review of sexual risk among pregnant and mothering teens in the USA: Pregnancy as an opportunity for integrated prevention of STD and repeat pregnancy. Social Science & Medicine. 2005;60:661-678.
- Cooksey CM, Berggren EK, Lee J. Chlamydia trachomatis infection in minority adolescent women: A public health challenge. Obstetrical & Gynecological Survey. 2010;65(11):729-735.