This page is general health information, not medical advice. It cannot tell you whether you have an infection. A clinician can, and the testing options on this site are a good place to start.

If you are looking at STD rates for Denver, you are probably trying to answer one of three questions. How common are these infections here? Is it getting better or worse? And what can a person actually do about it?

This guide takes those questions one at a time. It uses published figures from the Centers for Disease Control and Prevention (CDC), the Colorado Department of Public Health and Environment rules, and the Public Health Institute at Denver Health, which runs Denver's public sexual health clinic. Every number comes with its year and its source. Where a current Denver figure is not published in the sources we checked, we say so instead of filling the gap.

Rates are about populations, not individuals. A high or low number for a city says nothing about whether any one person has an infection. Only a test, read by a clinician, can tell you that.

How to read STD rates: counts, rates and what they miss
Colorado's latest numbers (CDC, 2023)
Denver's published figures and what is missing
STD rates by state and by city: how to compare fairly
What drives the trends
Free and low-cost testing in Denver
Sources

Key takeaways

CDC's 2023 state tables list Colorado at 435.1 chlamydia cases per 100,000 people, 128.7 gonorrhea cases per 100,000, and 16.0 primary and secondary syphilis cases per 100,000.
The same CDC tables count 51 congenital syphilis cases in Colorado in 2023, a rate of 81.8 per 100,000 live births.
The most recent Denver city figures in the sources we checked are preliminary 2018 estimates from Denver Public Health. They are old, and they should not be read as today's numbers.
A published rate reflects who gets tested and reported as well as who is infected, so rising numbers can mean more infection, more testing, or both.
Most bacterial STIs are curable with treatment from a clinician. HIV and herpes are not curable but are treatable.
Free and low-cost testing is available in Denver, including free walk-in outreach testing and a clinic with a sliding fee scale of $0 to $70.

How to read STD rates: counts, rates and what they miss

STD rates look simple, but three details change what they mean. Knowing them makes every table in this guide easier to read.

A count is not a rate

A count is the number of reported cases. A rate divides that count by the size of the population, usually per 100,000 people. Rates let you compare a large place with a small one. A county with 5,000 cases and a million residents is not necessarily in a worse position than a county with 500 cases and 50,000 residents.

Some of the Denver figures below are counts only. When a source gives no rate, we do not calculate one ourselves.

Rates describe reported cases, not all infections

Public health agencies count what is diagnosed and reported. Many STIs cause no symptoms, so people can carry them without knowing. The CDC notes in its STI Treatment Guidelines (2021) that screening is how most of these infections are found. That means published numbers are almost always an undercount of true infection.

More testing can raise the number

If a city expands screening, it will find more infections that were already there. A rising rate can therefore reflect better access to testing as well as spread. Analysts look at several years together, and at several infections at once, before drawing conclusions.

Reporting is required, and it is how the numbers exist

Colorado's disease reporting rules (6 CCR 1009-1, Appendix A, published by the Colorado Secretary of State) set the clock for labs and providers:

Chlamydia and gonorrhea at any body site are reportable within 4 days.
Positive syphilis results are reportable within 1 working day, and laboratories also report negative results.
HIV and AIDS laboratory data, including CD4 counts and viral load, are reportable within 4 days.

These reports go to public health for tracking and follow-up. They are the raw material for every rate in this guide.

Colorado's latest numbers (CDC, 2023)

The most recent complete state-level figures in the sources we checked come from the CDC's 2023 STI Surveillance State Ranking Tables. CDC had not finalized 2024 state tables at the time of research.

Infection (Colorado, 2023)	Cases	Rate	CDC rank in table
Chlamydia	25,571	435.1 per 100,000	31
Gonorrhea	7,563	128.7 per 100,000	35
Syphilis, primary and secondary	938	16.0 per 100,000	22
Congenital syphilis	51	81.8 per 100,000 live births	21

Source: CDC, 2023 STI Surveillance State Ranking Tables (Tables 28, 19, 9 and 4).

Chlamydia

Chlamydia is the most commonly reported infection in the table. Colorado recorded 25,571 cases in 2023, or 435.1 per 100,000 people, according to CDC. Chlamydia is curable with treatment from a clinician. It often causes no symptoms, which is why the CDC and the US Preventive Services Task Force (USPSTF) recommend routine screening for sexually active women under 25 and for older women with risk factors.

Gonorrhea

CDC's 2023 table lists 7,563 gonorrhea cases in Colorado, a rate of 128.7 per 100,000. Gonorrhea is also curable with treatment, and a clinician chooses the medicine. The CDC STI Treatment Guidelines (2021) explain that treatment choices have changed over time as the bacteria have become resistant to some antibiotics. That is one reason to let a clinician decide, rather than relying on old advice.

Syphilis

CDC counted 938 primary and secondary syphilis cases in Colorado in 2023, a rate of 16.0 per 100,000. Primary and secondary are the early stages. Syphilis is curable with treatment from a clinician, and it is much easier to treat early. Because it can be quiet for long stretches, a blood test is the way it is found.

Congenital syphilis

Congenital syphilis happens when syphilis passes from a pregnant person to a baby. CDC's 2023 table lists 51 Colorado cases, or 81.8 per 100,000 live births. Denver Health separately reported 50 cases for the state in 2023, and we use the CDC figure here for consistency. Congenital syphilis is preventable when a pregnant person is tested and treated in time. More on that in the section on testing.

A note on the rank column

The rank column shows where CDC's table places Colorado among the states for each measure. Ranks can shift a few places when a rate moves slightly, so they are best read as context, not a verdict.

Denver's published figures and what is missing

Denver County is also the City of Denver, so city and county figures are the same place. The Public Health Institute at Denver Health, which operates Denver Public Health, published preliminary city estimates in April 2019 for the year 2018. They remain the most recent city-level numbers we could verify.

Infection (Denver, 2018, preliminary)	Estimated cases	Change over four years
Chlamydia	About 7,317	Up 24%
Gonorrhea	About 2,703	Up 150%
Syphilis, all stages	405 new cases	Up 75%

Source: Public Health Institute at Denver Health, "Rate of STDs in Denver continues to climb," April 30, 2019.

How to read these figures responsibly

These are counts, not rates, and they are preliminary. The syphilis figure covers all stages, so it is not directly comparable with the primary and secondary figure in the state table above. Most important, the Denver numbers are from 2018 and the Colorado numbers are from 2023. They describe different years, and they should not be set side by side as if one place were higher than the other.

What the 2018 report does show is direction. Denver Public Health described rising diagnoses of all three infections over the four years before 2018, with the sharpest increase in gonorrhea.

What we could not find

Several figures a reader might expect were not available in the sources we checked:

Denver County rates for 2023 or 2024 for any of these infections.
Denver primary and secondary syphilis figures.
Denver congenital syphilis figures.
New HIV diagnoses for Denver or for Colorado.

We are not estimating these. For current local figures, contact the Public Health Institute at Denver Health through its STD testing and treatment page, or ask the Colorado health department for its latest surveillance report. CDC also publishes county-level data through its AtlasPlus tool, which is worth checking for newer years.

STD rates by state and by city: how to compare fairly

People often search for STD rates by state or STD rates by city to see how their home stacks up. The comparison can be useful, but only if it is done carefully.

Comparing states

CDC's annual state ranking tables are the cleanest source for STD rates by state. Every state is measured the same way, for the same year, per 100,000 people. That is why this guide leans on them for Colorado.

Even so, state averages hide a lot. A state includes dense cities, small towns and rural counties, and the numbers are often very different between them. A state rate also depends on how many people are screened and how completely cases are reported.

Comparing cities

STD rates by city are harder. Cities publish on different schedules, use different age groups, and sometimes count preliminary rather than final cases. A city that tests more people can look worse than a city that tests fewer, even if actual infection levels are similar.

When you see a ranking of cities, check four things before trusting it:

Is it a rate per 100,000 or a raw count?
Do all the cities use the same year?
Are the figures final or preliminary?
Does the source say how cases were counted?

If the answer to any of these is unclear, treat the comparison as a rough picture only.

What this means for a Denver reader

For Denver, the honest answer is that the most recent verified city numbers are older than the state ones. The 2023 CDC state tables are the best current benchmark. For a more current local picture, ask Denver Public Health or check CDC's county-level data.

What drives the trends

No single cause explains why STI numbers move. Public health agencies, including CDC, point to a mix of factors. We describe the general picture here and do not attribute any one cause to Denver specifically, because the sources we reviewed do not.

Many infections are silent

Chlamydia, gonorrhea and early syphilis often cause no symptoms, or symptoms that are easy to miss. Without screening, an infection can continue and be passed to others without anyone knowing. This is the main reason CDC and USPSTF emphasize routine screening instead of waiting for symptoms.

Testing and reporting change the count

When more people are tested, more cases are found. When clinics are closed, stretched thin or hard to reach, fewer are found, and the number can look lower than the truth. Over several years, changes in testing can be mistaken for changes in infection. This is why analysts compare multiple years and several infections together.

Access to care

Cost, insurance, transportation, work schedules and language all affect whether someone can get tested and treated. Free and low-cost options, walk-in outreach and testing in more than one language help close those gaps. Denver's outreach program offers testing in English and Spanish, according to Denver Public Health.

Prevention tools are expanding

Prevention has grown beyond condoms. Pre-exposure prophylaxis (PrEP) lowers the chance of getting HIV, and post-exposure prophylaxis (PEP) is used after a possible HIV exposure. In 2024 CDC issued guidance on doxycycline post-exposure prophylaxis, or doxy-PEP, for certain groups, including gay and bisexual men and transgender women who have had a bacterial STI in the past year. Whether any of these tools fit a person is a conversation for a clinician, who also decides the medicine and how to take it.

The Denver Sexual Health Clinic's page does not state that it offers doxy-PEP, so ask when you call.

Syphilis in pregnancy

Colorado has specific rules because of congenital syphilis. Under Colorado's Regulation 12 (6 CCR 1009-1), providers and facilities treating a pregnant person must offer syphilis testing at the first prenatal visit or in the first trimester, again in the third trimester at 28 to 32 weeks, and at delivery. A test is also offered after a fetal death after 20 weeks. The exception is when a documented test already met the requirement or the patient declines.

The Colorado General Assembly's HB24-1456, signed June 5, 2024, directs the State Board of Health to set prenatal syphilis testing standards by rule. If you are pregnant, ask your prenatal provider about the testing schedule that applies to you.

Stigma and silence

Shame keeps people from getting tested, and that is a public health problem in its own right. STIs are common, they are medical conditions, and anyone of any gender or orientation can get one. Testing is a routine part of health care, not a judgment.

Free and low-cost testing in Denver

Numbers matter most when they lead to action. Denver has several ways to get tested. For a fuller breakdown of locations and costs, see our guide to where to get tested in Denver and what it costs.

Denver Sexual Health Clinic

Operated by the Public Health Institute at Denver Health, the clinic is at 660 N. Bannock St., Pavilion L, 2nd Floor, Denver, CO 80204. The phone number is 303-602-3540.

Appointments: required for all clinic visits.
Hours: Monday through Friday, 8 a.m. to 5 p.m. The clinic is closed from 8 to 9 a.m. on the second Monday of each month.
Cost: people who are uninsured or out of network pay on a sliding fee scale of $0 to $70. Denver Public Health says no one is denied care based on ability to pay.
Services: STD, HIV and hepatitis C testing, PrEP, PEP and treatment.
Testing-only visits: these are limited to gonorrhea, chlamydia, syphilis, HIV and hepatitis C. People with symptoms need a provider visit.
PEP: if you may have been exposed to HIV in the past 72 hours, call as soon as possible.

Denver Health community outreach testing

Denver Public Health runs free, confidential walk-in testing for STIs, HIV and hepatitis C at rotating community locations around the Denver metro area. Testing is offered in English and Spanish. There is no single street address, so call or text 720-415-7075 for current locations. The outreach team does not provide physical exams or treatment. If you have symptoms or a known exposure, contact the Denver Sexual Health Clinic instead.

HeyDenver (Colorado Health Network)

HeyDenver is at 822 E 19th Ave, Denver, CO 80218. The phone number is 303-962-2880. Office hours are Monday through Friday, 9 a.m. to 4 p.m. Testing includes chlamydia and gonorrhea, rapid HIV, rapid syphilis, and hepatitis C case by case, plus PrEP navigation.

The program's page describes its STI testing as free in its Spanish heading but does not state a price in the English text. Walk-in testing happens on set days. Colorado Health Network's own listing shows this site as testing by appointment, so confirm the schedule before you go. Details are on the HeyDenver website.

Planned Parenthood of the Rocky Mountains, Park Hill Health Center

The center is at 7155 E 38th Ave, Denver, CO 80207, phone (303) 321-2458. The CDC GetTested directory lists STD and HIV testing, rapid HIV testing, hepatitis C testing, HPV vaccine and PrEP, with insurance and Medicaid accepted and no appointment needed. The listing does not publish prices or hours, so call to ask about eligibility and fees. See the CDC GetTested listing.

Clinica Tepeyac

Clinica Tepeyac is at 2101 E 48th Ave, Denver, CO 80216, phone (303) 458-5302. The CDC GetTested listing shows a sliding scale, insurance and Medicaid accepted, HPV vaccine and PrEP, and appointments required. Hours are not published there, so call first. See the CDC GetTested listing.

STRIDE Community Health Center, Oneida

STRIDE is at 2255 S Oneida St, Denver, CO 80224, phone 303-778-7433, open Monday through Friday, 7 a.m. to 5:30 p.m. STRIDE's women's health page lists STI testing and treatment, but the Oneida location page itself does not mention it, and no price is published. Call to confirm what is offered. See STRIDE's Oneida page.

Free mail-in testing from Denver Public Health

TestYourselfColorado.com, provided by Denver Public Health, offers free mail-in chlamydia and gonorrhea testing and an at-home HIV test once a year for Colorado residents age 18 or older. It is not for people who are pregnant or who have symptoms. More frequent testing every three months is available at low cost, and treatment is free, according to the site. Visit TestYourselfColorado.com.

Testing for people under 18

Under Colorado law (C.R.S. 25-4-409), a health care provider must, at a minor's request, perform an exam for a sexually transmitted infection, treat if needed, and discuss or prescribe preventive measures. Parental consent is not required, and the information is kept confidential except for child protection reporting. The statute sets no minimum age. For a minor 13 or younger, the provider may involve a parent or guardian.

Finding other options

CDC's GetTested locator lets you look up STD, HIV and hepatitis testing sites by ZIP code, including ones not listed here.

What to expect and what to ask

A clinician decides which tests fit your situation based on your history, symptoms and the kinds of contact you have had. Some infections can take time to show up on a test. CDC publishes window periods for each infection, and a clinician can tell you whether and when to retest. Two questions are worth asking at any visit:

Which infections will this visit test for, and which will it not?
If something is found, how is treatment handled, and who contacts me?

If a result is positive for a bacterial infection or trichomoniasis, treatment from a clinician cures it. For HIV and herpes, a clinician can prescribe treatment that manages the condition. Partners may also need testing, and the clinic can explain how that works in Colorado.

STD Rates in Denver: What the Latest Data Shows

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