Introduction

The U.S. STI epidemic is changing, but it has not resolved. Provisional CDC 2024 national surveillance data show declines in reported chlamydia, gonorrhea, and primary and secondary syphilis compared with 2023. That progress is clinically meaningful, but it should not be overread. The combined burden of chlamydia, gonorrhea, and syphilis remains substantial, congenital syphilis continues to rise, and state-level variation remains large.

The geography of STI risk matters because statewide averages can obscure local sexual networks, county-level hot spots, testing access, and age-specific differences. A high case count may reflect population size, while a high rate per 100,000 population may reflect a smaller state with concentrated transmission. Both metrics matter, but they answer different questions. Clinicians, pharmacists, and public health teams should avoid using a state rank as a direct proxy for individual risk after a single exposure.

This article reviews the major reportable STIs, addresses important nonreportable or incompletely reported infections, summarizes emerging resistance and pathogen threats, and proposes a transparent framework for state-level exposure-risk modeling.

Methods and Data Sources

The strongest state-level U.S. surveillance data are available for chlamydia, gonorrhea, syphilis, congenital syphilis, and HIV. CDC 2024 STI data are provisional and national-level only. Therefore, this article uses 2024 CDC data for national trends and finalized 2023 CDC state-ranking tables for state-level comparisons. CDC AtlasPlus is identified as the appropriate source for future extraction of detailed state-by-age, sex, race/ethnicity, and county-level tables.

The following infections are covered:

1. Routinely reportable STIs with strong state-level surveillance: chlamydia, gonorrhea, syphilis, and congenital syphilis.

2. HIV, which has separate CDC surveillance and prevention infrastructure.

3. Common but incompletely state-reportable STIs: HPV, HSV-1, HSV-2, trichomoniasis, and Mycoplasma genitalium.

4. Sexually associated or network-associated infections: lymphogranuloma venereum, mpox in sexual networks, hepatitis B, hepatitis C in selected sexual networks, and sexually transmitted enteric pathogens such as Shigella.

A key methodological point is that reported cases are not equivalent to true incidence or prevalence. Reported rates depend on infection burden, testing availability, screening practices, symptoms, public health infrastructure, reporting completeness, and access to care.

National Trends: Progress With Persistent Burden

CDC’s provisional 2024 data reported 1,515,985 chlamydia cases, 543,409 gonorrhea cases, 190,242 total syphilis cases, 41,496 primary and secondary syphilis cases, and 3,941 congenital syphilis cases. The combined total of chlamydia, gonorrhea, and total syphilis declined from 2023 to 2024, but overall cases remain higher than a decade earlier.

Chlamydia

Chlamydia remains the most commonly reported bacterial STI in the United States. The national 2024 rate was 445.7 per 100,000 population, down from 492.2 in 2023. Chlamydia is often asymptomatic, especially in women, and reported rates are strongly influenced by screening patterns. A decline in reported cases may reflect true reduction, reduced testing, changing screening practices, or a combination of these factors.

Gonorrhea

Gonorrhea declined nationally in 2024, with 543,409 reported cases and a rate of 159.8 per 100,000 population. Gonorrhea remains clinically important because it can cause urethritis, cervicitis, pelvic inflammatory disease, epididymitis, infertility, adverse pregnancy outcomes, disseminated infection, and increased susceptibility to HIV. Its central public health threat is antimicrobial resistance.

Syphilis

Total syphilis remained high in 2024 despite a decline in primary and secondary syphilis. Primary and secondary syphilis are the most infectious stages and declined from 53,007 cases in 2023 to 41,496 in 2024. However, total syphilis includes early non-primary non-secondary syphilis, late or unknown-duration syphilis, and congenital syphilis. The continued burden of later-stage and congenital disease indicates persistent diagnostic and public health gaps.

Congenital Syphilis

Congenital syphilis is a sentinel marker of failure in prenatal screening, treatment, partner services, and public health follow-up. CDC reported 3,941 congenital syphilis cases in 2024, a continued increase. Because congenital syphilis is preventable with timely screening and penicillin treatment, rising congenital cases should be treated as a clinical and systems-level emergency.

State-Level Burden: Rates Tell a Different Story Than Counts

The highest-burden states vary depending on whether the metric is total cases or population-adjusted rate. Population-heavy states such as California, Texas, Florida, and New York often rank high by total case count. Smaller states can rank much higher by rate, indicating more intense transmission relative to population size.

Top States by Rate, 2023

Infection	Highest-rate states	Clinical interpretation
Chlamydia	Louisiana, Mississippi, Alaska, Alabama, Georgia	Young adults and screening access strongly influence rates.
Gonorrhea	Alaska, Louisiana, Georgia, South Dakota, Mississippi	Reflects high transmission intensity and testing patterns.
Primary and secondary syphilis	South Dakota, New Mexico, Mississippi, Arkansas, Alabama	Indicates concentrated infectious syphilis transmission.
Congenital syphilis	South Dakota, New Mexico, Mississippi, Arizona, Texas	Reflects prenatal screening and treatment failures, not only adult STI burden.

Top States by Total Reported Cases, 2023

Infection	States with largest case counts	Why this matters
Chlamydia	California, Texas, Florida, New York, Georgia	Large populations drive clinical and public health workload.
Gonorrhea	California, Texas, Florida, New York, Georgia	High total cases affect antimicrobial use and partner services.
Primary and secondary syphilis	California, Texas, Florida, New York, Georgia	Urban networks and large populations contribute heavily.
Congenital syphilis	Texas, California, Florida, Arizona, Mississippi	High counts require obstetric and public health capacity.

A Practical 50-State Burden Tier

The following tier system is derived from finalized 2023 CDC state-ranking data for chlamydia, gonorrhea, primary and secondary syphilis, and congenital syphilis. It is not a personal risk estimate. It is a surveillance-based way to interpret state-level background burden.

Tier	States	Interpretation
Very high burden	Alaska, Louisiana, Mississippi, South Dakota	Multiple high-rate bacterial STI signals or extreme syphilis burden.
High burden	Alabama, Arkansas, Georgia, New Mexico, North Carolina	High rates in at least one major bacterial STI category.
Moderate burden	Arizona, California, Delaware, Florida, Illinois, Maryland, Missouri, Nevada, New York, Oklahoma, South Carolina, Tennessee, Texas	Important state-level burden, often driven by population size, regional transmission, or congenital syphilis.
Lower to moderate burden	Colorado, Hawaii, Indiana, Kansas, Kentucky, Massachusetts, Michigan, Montana, Nebraska, North Dakota, Ohio, Oregon, Rhode Island, Virginia, Washington	Statewide rates below the highest-burden jurisdictions, but local hot spots may still be substantial.
Lower burden	Connecticut, Idaho, Iowa, Maine, Minnesota, New Hampshire, New Jersey, Pennsylvania, Utah, Vermont, West Virginia, Wisconsin, Wyoming	Lower statewide reported rates, but individual risk may still be high in specific networks or counties.

This table should not be used to reassure a patient after a known exposure. A person exposed to an infected partner has risk regardless of state tier.

Age-Specific Risk Patterns

Age is one of the strongest predictors of reported chlamydia and gonorrhea risk. CDC and USPSTF guidance consistently recognizes adolescents and young adults as high-burden populations for chlamydia and gonorrhea screening, especially sexually active women 24 years or younger. The risk profile changes across the lifespan.

Age group	Dominant STI concerns	Clinical interpretation
15–19	Chlamydia, gonorrhea, HPV	Screening access, confidentiality, and prevention counseling are central.
20–24	Chlamydia, gonorrhea, HPV, HSV	Often the highest-burden age band for bacterial STIs.
25–29	Chlamydia, gonorrhea, syphilis, HIV in some networks	Risk becomes more network- and partner-specific.
30–44	Syphilis, HIV, HSV, HPV sequelae	Rates may be lower for chlamydia but substantial for syphilis and HIV in affected networks.
45 and older	HSV, HPV-related disease, syphilis in selected networks, HIV	Lower average bacterial STI rates do not eliminate risk; testing should follow exposure and risk history.

A final state-age quantitative appendix would require extraction from CDC AtlasPlus or state health department datasets by state, infection, age group, sex, and year. Without that extraction, a precise state-by-age single-exposure risk table would create false precision.

Emerging and More Clinically Concerning STI Threats

Antimicrobial-Resistant Gonorrhea

Neisseria gonorrhoeae is the most important antimicrobial-resistance threat among common STIs. The organism has developed resistance to multiple historical therapies, including sulfonamides, penicillin, tetracyclines, fluoroquinolones, and macrolides. In the United States, ceftriaxone remains the only CDC-recommended first-line treatment for uncomplicated urogenital, anorectal, and pharyngeal gonorrhea.

GISP data through 2024 remain reassuring for ceftriaxone susceptibility, with elevated ceftriaxone MICs uncommon. That should not lead to complacency. Ciprofloxacin resistance remains common, azithromycin reduced susceptibility has been clinically important, and international reports of ceftriaxone-resistant strains demonstrate the potential for future U.S. importation or emergence.

Clinical implications include using CDC-recommended ceftriaxone regimens, treating chlamydia when it has not been excluded, obtaining culture and antimicrobial susceptibility testing when treatment failure is suspected, and promptly reporting suspected cephalosporin treatment failure.

Mycoplasma genitalium

Mycoplasma genitalium is increasingly recognized in persistent or recurrent urethritis and cervicitis and may contribute to pelvic inflammatory disease. The central concern is antimicrobial resistance. CDC recommends two-stage therapy, ideally resistance-guided. If macrolide resistance testing is available, doxycycline is followed by azithromycin for macrolide-susceptible infection or moxifloxacin for macrolide-resistant infection. If resistance testing is unavailable and M. genitalium is detected, doxycycline followed by moxifloxacin is recommended.

M. genitalium is not uniformly reported by state, so it should not be included in a 50-state numeric risk table unless a jurisdiction has reliable local surveillance data.

Extensively Drug-Resistant Shigella and Sexually Transmitted Enteric Pathogens

Shigella is not traditionally classified as an STI, but sexual transmission has become important in some networks, particularly among MSM. CDC has warned about extensively drug-resistant shigellosis, including sexual transmission and co-occurrence with HIV and other STIs. Clinicians should take a sexual history when shigellosis is suspected and use culture and susceptibility testing when antibiotics are indicated.

Congenital Syphilis

Congenital syphilis is not a new strain, but it is one of the most severe STI-related public health failures. It reflects missed opportunities for prenatal care, syphilis testing, treatment, partner services, and follow-up. Preventing congenital syphilis requires early screening, repeat screening when indicated, timely penicillin treatment, and public health coordination.

HPV

HPV is the most common STI in the United States, but it is not reported as a state-level incident case disease in the same way as chlamydia, gonorrhea, or syphilis. CDC estimates that more than 42 million Americans are infected with disease-associated HPV types and that about 13 million new infections occur each year. HPV risk is better assessed through vaccination coverage, cervical cancer screening, HPV-associated cancer epidemiology, and individual exposure history.

HSV

HSV-1 and HSV-2 are common, lifelong infections. NHANES 2015–2016 data estimated HSV-1 seroprevalence at 47.8% and HSV-2 seroprevalence at 11.9% among persons aged 14–49. HSV is not uniformly reportable by state. Routine serologic screening of asymptomatic low-risk patients is generally not recommended because of test-performance and psychosocial concerns.

Trichomoniasis

Trichomoniasis is common but not nationally reportable in the same manner as chlamydia, gonorrhea, or syphilis. CDC treatment guidelines cite population-based U.S. prevalence estimates of approximately 2.1% among women and 0.5% among men, with important disparities. State-level single-exposure risk modeling is not reliable without local prevalence data.

Treatment and Drug-Safety Considerations

This article is not a treatment monograph, but several drug-safety points are relevant to public health recommendations.

Drug or strategy	Role	Key safety or implementation issue
Ceftriaxone	First-line CDC-recommended treatment for uncomplicated gonorrhea	Avoid in patients with known cephalosporin hypersensitivity; neonatal calcium-related contraindications apply in labeling.
Doxycycline	Treatment for chlamydia and part of doxy-PEP strategy in selected populations	Counsel regarding gastrointestinal intolerance, esophagitis prevention, photosensitivity, drug interactions with polyvalent cations, and pregnancy/tooth-development cautions.
Moxifloxacin	Used for M. genitalium when indicated	Fluoroquinolone boxed warnings include tendon rupture, peripheral neuropathy, CNS effects, and other serious risks; use should be guideline-driven.
Penicillin G	Treatment of syphilis and required therapy for syphilis in pregnancy	Penicillin allergy in pregnancy requires specialist management and desensitization when syphilis treatment is needed.
Doxy-PEP	Prevention strategy for selected MSM and transgender women with recent bacterial STI	CDC recommends shared decision-making, 200 mg within 72 hours after sex, not exceeding 200 mg per 24 hours, with STI testing every 3–6 months.

Why Single-Exposure Risk Cannot Be Read From a State Table

A state’s reported rate is an annual surveillance measure, not the probability of infection from one sexual act. For example, a rate of 500 cases per 100,000 population does not mean a 0.5% chance of acquisition from a single exposure. A single-exposure estimate depends first on whether the partner is infected at that moment.

A defensible model must include:

1. Partner infection prevalence in the relevant age, sex, geography, and network.

2. Per-act transmission probability by pathogen and exposure type.

3. Exposure route: vaginal, anal, oral, insertive, or receptive.

4. Partner treatment status, symptoms, and recent testing.

5. Condom use, PrEP, vaccination, HIV viral suppression, and other prevention modifiers.

6. Local testing and reporting bias.

7. Uncertainty intervals.

The basic model is:

Estimated single-exposure risk = probability partner is infected x per-act transmission probability x exposure-route modifier x prevention modifiers x uncertainty adjustment

This model should return ranges, not precise point estimates.

Per-Act Transmission Inputs for Modeling

Infection	Modeling status	Use in state-level estimates
Chlamydia	Per-act estimates vary across models; per-partnership estimates are more stable.	Use broad low/base/high ranges only.
Gonorrhea	Transmission can be efficient, especially from infected male to female partner; anatomic site matters.	Use exposure-specific ranges and avoid false precision.
Syphilis	Depends on contact with infectious lesions and disease stage.	Model only with lesion-stage assumptions.
HIV	Per-act estimates are available by exposure type when the partner has transmissible HIV.	Adjust for viral suppression, PrEP, condoms, and partner status.
HPV	Common and transmitted by skin-to-skin genital contact.	Do not model precisely by state from case reports.
HSV	Depends on HSV type, shedding, symptoms, antivirals, and sex direction.	Use qualitative or partner-status-based scenarios.
Trichomoniasis	Prevalence data exist, but per-act estimates are limited.	Use scenario-based estimates only.
Hepatitis B	Strongly modified by vaccination and partner infectivity.	Model by vaccination status and partner status.
Hepatitis C	Sexual transmission risk is concentrated in specific networks and blood-exposure contexts.	Do not generalize by state for low-risk heterosexual exposure.

State-by-Age Risk Framework

The final risk tool, if developed, should combine the state burden tier with age-specific and exposure-specific modifiers. A reasonable framework is shown below.

State burden tier	Age 15–24	Age 25–34	Age 35+
Very high burden	Highest background risk for chlamydia and gonorrhea; syphilis risk depends on network	High background bacterial STI risk; syphilis and HIV require network-specific assessment	Risk lower on average but remains high with affected partners or networks
High burden	High background risk, especially for chlamydia and gonorrhea	Moderate to high risk depending on partner network	Exposure-specific risk remains clinically relevant
Moderate burden	Moderate background risk; local hot spots may be high	Risk driven more by partner and network than state average	Testing should follow exposure and risk history
Lower burden	Lower statewide background rates but not low individual risk after known exposure	Partner status dominates risk	State tier should not be used to defer testing after exposure

This framework is appropriate for publication. A numeric 50-state single-exposure table should be published only after formal data extraction and model validation.

Clinical and Public Health Implications

STI prevention should be layered rather than dependent on any single intervention. Screening remains central, particularly for sexually active women 24 years or younger, pregnant patients, MSM, transgender women, persons with HIV, and patients with new or multiple partners. NAAT testing should be performed at exposed anatomic sites when clinically indicated.

Prevention should include condoms, HIV PrEP when indicated, HIV treatment and viral suppression, HPV vaccination, hepatitis B vaccination, doxy-PEP in CDC-recommended populations, partner notification, expedited partner therapy where legal and appropriate, retesting after treatment when guideline-recommended, and public health follow-up for syphilis and congenital syphilis.

Public health programs should prioritize high-rate jurisdictions, but clinical care should remain exposure-specific. A patient in a lower-burden state may still have high risk after exposure to an infected partner, while a patient in a high-burden state may have low risk in a mutually monogamous relationship with recent negative testing.

Risk Calculator:

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