By Here is something most people don’t know: the United States has some of the highest rates of sexually transmitted infections of any high-income country in the world. Not because Americans are doing anything particularly unusual — but because the combination of inconsistent sex education, fragmented healthcare access, stigma around testing, and the asymptomatic nature of most STIs creates conditions where infections spread quietly and widely.
The CDC estimates approximately 26 million new STI cases occur in the US every year (CDC, 2021). That number includes people of every age, relationship status, income level, and sexual orientation. STIs do not discriminate. And because the majority of them produce no obvious symptoms, most people who have one don’t know it.
This is not an article designed to alarm you. It’s designed to give you accurate, practical information about what the most common STIs are, how they spread, what they do if untreated, how testing works in the US, and what treatment looks like. That information exists to help you make informed decisions — not to generate anxiety.
This article is part of our Sexual Health series. For the full foundation, visit our Sexual Health Explained guide.
Why STIs Are So Commonly Missed
Before getting into the specifics of each infection, it’s worth understanding why STIs are so frequently undiagnosed — because that context changes how you think about testing.
Most STIs are either entirely asymptomatic or produce symptoms so mild that they’re easily attributed to something else. Chlamydia, the most commonly reported bacterial STI in the US, produces no symptoms in approximately 70 to 95 percent of cases in women and 50 percent of cases in men (CDC, 2023). Gonorrhea is similarly silent in many people. Even HIV, during the acute infection phase, produces symptoms that most people mistake for a flu. Genital herpes frequently causes outbreaks so mild that people don’t recognize them as herpes at all.
The result is that transmission happens constantly between people who are entirely unaware they’re infected. Regular testing isn’t a response to symptoms — it’s the only way to actually know your status.
“Most STIs produce no symptoms at all. Regular testing isn’t something you do because you’re worried about a symptom — it’s the only way to actually know what’s going on.”
The Most Common STIs in the United States
Human Papillomavirus (HPV)
HPV is the most common sexually transmitted infection in the United States — so common that the CDC estimates most sexually active adults will have it at some point in their lives (CDC, 2023). There are more than 200 strains of HPV, and they range widely in their consequences.
Most HPV infections clear on their own within one to two years without causing any health problems. The immune system handles them the same way it handles other viral infections. But certain high-risk strains — particularly HPV 16 and 18 — are responsible for the majority of cervical cancers, as well as cancers of the anus, throat, penis, vulva, and vagina. Low-risk strains, particularly HPV 6 and 11, cause genital warts.
There is no treatment for HPV itself. Treatment addresses the conditions it causes — abnormal cervical cells (through procedures like LEEP or cryotherapy), genital warts, and in advanced cases, cancer. The most powerful tool against HPV is prevention through vaccination. The HPV vaccine — Gardasil 9 — is recommended in the US for preteens aged 11 to 12 but is approved and effective through age 45 for people who weren’t previously vaccinated. It protects against the strains responsible for the majority of HPV-related cancers and genital warts.
Regular Pap smears and HPV co-tests for people with a cervix remain essential because they detect cervical cell changes caused by HPV before they progress to cancer.
Chlamydia
Chlamydia is the most commonly reported bacterial STI in the United States, with over 1.6 million cases reported to the CDC in 2021 — and the actual number significantly higher due to underdiagnosis (CDC, 2023).
It spreads through vaginal, anal, and oral sex. Most people have no symptoms, which is precisely what makes it so prevalent. When symptoms do occur in women, they can include unusual discharge, burning during urination, and pelvic pain. In men, symptoms may include discharge from the penis, burning urination, and testicular pain.
The consequences of untreated chlamydia are significant, particularly for women. It can progress to pelvic inflammatory disease (PID), a serious infection of the reproductive organs that can cause chronic pelvic pain, ectopic pregnancy, and infertility. The good news is that chlamydia is easily cured with a single dose or short course of antibiotics — typically azithromycin or doxycycline. The challenge is getting people tested before complications develop.
The CDC recommends annual chlamydia testing for all sexually active women under 25, and for older women with new or multiple partners. Men who have sex with men should be tested at least annually.
Gonorrhea
Gonorrhea is the second most commonly reported bacterial STI in the US, with approximately 700,000 cases reported annually — and actual incidence estimated to be significantly higher (CDC, 2023). Like chlamydia, it frequently produces no symptoms and can quietly cause serious reproductive consequences if untreated.
When symptoms occur, they typically appear two to seven days after exposure. In women, symptoms may include increased vaginal discharge and pelvic pain — often mistaken for a bladder infection. In men, symptoms include a yellow or green discharge from the penis and painful urination. Rectal infection, which can occur in both men and women, often causes no symptoms or mild rectal discomfort.
Untreated gonorrhea can cause PID in women, epididymitis in men, and increases the risk of HIV transmission. It can also spread to the blood and joints, causing disseminated gonococcal infection — a serious but relatively uncommon complication.
A significant and growing concern with gonorrhea is antibiotic resistance. The bacteria has developed resistance to multiple antibiotic classes over decades, and the current recommended treatment — ceftriaxone injected intramuscularly — represents one of the last reliable options. Emerging resistance to ceftriaxone is being monitored closely by public health authorities.
Genital Herpes (HSV-1 and HSV-2)
Genital herpes is caused by herpes simplex virus — either HSV-1 (more commonly associated with oral herpes but increasingly a cause of genital infections) or HSV-2. Approximately one in six Americans aged 14 to 49 has genital herpes, making it remarkably prevalent (CDC, 2023). Because many people have mild or no symptoms and many are never tested, the true number is likely higher.
Herpes spreads through skin-to-skin contact, including during sex — and importantly, it can be transmitted even when no sores or symptoms are present, through a process called asymptomatic viral shedding. This is why herpes transmission is so common even among couples who are careful.
Initial outbreaks, when they occur, can involve painful sores or blisters in the genital area, flu-like symptoms, and swollen lymph nodes. Recurrent outbreaks are typically milder and shorter. Over time, many people experience fewer and less severe outbreaks. Some people have a single outbreak and never experience another. Others have frequent recurrences.
There is no cure for herpes. Antiviral medications — acyclovir, valacyclovir, famciclovir — don’t eliminate the virus but significantly reduce outbreak frequency, duration, and severity. Daily suppressive therapy also reduces the risk of transmission to partners by approximately 50 percent.
One of the most important things to understand about herpes is that it is a common, manageable condition — not the devastating diagnosis that stigma suggests. Many people with herpes lead entirely normal sexual and romantic lives with appropriate precautions and open communication.
Syphilis
Syphilis is experiencing a significant resurgence in the United States. After declining for decades, rates have been rising sharply since the early 2000s, with reported cases increasing more than fourfold between 2015 and 2021 (CDC, 2023). Particularly alarming is the dramatic rise in congenital syphilis — infections passed from mother to baby during pregnancy — which can cause serious birth defects and infant death.
Syphilis progresses through stages if untreated, each with different presentations:
Primary syphilis produces a painless sore called a chancre at the site of infection — typically the genitals, anus, or mouth. Because it’s painless, it’s frequently missed.
Secondary syphilis occurs weeks to months later and produces a rash — classically on the palms and soles of the feet — along with flu-like symptoms and sometimes mouth sores.
Latent syphilis is a period with no symptoms but ongoing infection.
Tertiary syphilis, in people who go untreated for years, can cause serious damage to the heart, brain, and other organs.
The good news is that syphilis remains fully curable with penicillin, which has been effective against it for over seventy years. The challenge is testing and early detection, particularly given the painless nature of primary syphilis and the long asymptomatic latent phase.
HIV
Approximately 1.2 million Americans are currently living with HIV, and an estimated 13 percent of them don’t know their status (CDC, 2023). HIV attacks the immune system by targeting CD4 cells, gradually reducing the immune system’s ability to fight infection. Untreated HIV progresses to AIDS — acquired immunodeficiency syndrome — when the immune system is severely compromised.
The landscape of HIV has been transformed by treatment. Modern antiretroviral therapy (ART) is highly effective at suppressing the virus to undetectable levels. People living with HIV who take their medication consistently and achieve an undetectable viral load cannot sexually transmit the virus to their partners — a principle known as Undetectable equals Untransmittable, or U=U.
Pre-exposure prophylaxis — PrEP — is a once-daily medication (most commonly tenofovir/emtricitabine, sold as Truvada or Descovy) that reduces the risk of HIV infection through sex by approximately 99 percent when taken consistently. It is available through healthcare providers and is covered by most insurance plans. Post-exposure prophylaxis — PEP — is an emergency treatment taken within 72 hours of a potential HIV exposure that can prevent infection.
The CDC recommends at least one HIV test for all adults aged 13 to 64 as part of routine healthcare, with more frequent testing — at least annually — for people at higher risk.
STI Testing in the United States: A Practical Guide
Understanding what tests exist and what your routine physical actually includes is essential — because the gap between what people assume they’re being tested for and what they’re actually being tested for is enormous.
A routine physical exam does not include STI testing unless you specifically request it. A “full panel” means different things to different providers and may not include everything you expect. You need to be explicit about what you want to be tested for and why.
| STI | How it’s tested | Who should be tested routinely |
|---|---|---|
| Chlamydia | Urine sample or swab | All sexually active women under 25; older women with multiple partners; MSM annually |
| Gonorrhea | Urine sample or swab | Same as chlamydia |
| Syphilis | Blood test | MSM at least annually; pregnant women; anyone with new or multiple partners |
| HIV | Blood test or oral swab | All adults 13–64 at least once; high-risk individuals at least annually |
| Herpes (HSV) | Clinical diagnosis or swab of active sore | Not recommended as routine screening; tested when symptoms present |
| HPV | No test available for men; Pap smear and co-test for people with a cervix | Per cervical cancer screening guidelines |
| Hepatitis B and C | Blood test | Recommended for all adults at least once; more frequently for higher-risk individuals |
Where to get tested in the US includes your primary care physician, OB-GYN, Planned Parenthood, community health centers, local health department clinics, and at-home testing services including Everlywell, LetsGetChecked, and myLAB Box. Many of these are covered by insurance or available on a sliding scale based on income.
Prevention: What Actually Works
Prevention of STIs is most effective when it’s layered — no single method provides complete protection against all infections.
Condoms are the most effective barrier method for reducing STI transmission. When used correctly and consistently, male condoms reduce the risk of HIV transmission by approximately 85 percent and substantially reduce the risk of chlamydia, gonorrhea, syphilis, and other infections. They are less effective against infections transmitted through skin-to-skin contact not covered by the condom — including herpes and HPV — but still provide meaningful risk reduction.
Vaccination provides highly effective protection against HPV and hepatitis B. The HPV vaccine is recommended for preteens but is beneficial for unvaccinated adults up to age 45. Hepatitis B vaccination is recommended for all adults who haven’t been previously vaccinated.
PrEP for HIV is one of the most significant advances in HIV prevention in decades and is underutilized relative to how many people would benefit from it.
Regular testing is itself a prevention tool — because knowing your status and your partners’ status allows for informed decisions and early treatment that prevents onward transmission.
Open communication with partners about testing history and status, while not always comfortable, is one of the most effective practical risk-reduction strategies available.
“Prevention is most effective when it’s layered. No single strategy covers all risks — but combining regular testing, vaccination, condoms, and open communication with partners reduces risk more substantially than any one approach alone.”
The Stigma Problem
It’s worth addressing directly because it affects everything else: the stigma around STIs in the United States is significant, persistent, and causes real harm.
Stigma delays testing because people don’t want to think of themselves as someone who could have an STI. It delays treatment because people are ashamed to seek it. It prevents honest communication between partners. It discourages healthcare providers from asking about sexual health routinely. And it attaches a moral judgment to a set of infections that are, at their core, simply infections — transmitted through a normal human activity.
Chlamydia is not a character failing. Herpes is not a punishment. HIV is not a consequence of bad decisions. These are infections, and like other infections they are acquired through exposure, not through any particular personal quality.
Getting tested regularly, seeking treatment promptly, and communicating honestly with partners are signs of responsibility — not shame.
Frequently Asked Questions
Q: Do I need to get tested if I’m in a monogamous relationship?
If both partners have been tested comprehensively before the relationship became sexually exclusive, and neither has had other partners since, the ongoing transmission risk is low. If either partner hasn’t been recently and comprehensively tested, testing together before relying on monogamy for STI protection is the right approach. Some infections — including herpes — can be present and transmissible without either partner knowing, which is why testing before establishing exclusivity matters.
Q: Can I get an STI from oral sex?
Yes. Herpes, gonorrhea, syphilis, and HPV can all be transmitted through oral sex. Chlamydia can also be transmitted orally, though it’s less common. Condoms and dental dams reduce but do not eliminate risk during oral sex. This is an often-overlooked transmission route worth factoring into conversations about testing and prevention.
Q: How long after exposure should I wait to get tested?
It depends on the infection. HIV tests are most accurate four weeks or more after exposure, with a conclusive result at 45 days for most modern tests. Chlamydia and gonorrhea can be detected within one to two weeks of exposure. Syphilis takes about three weeks to show up on a blood test. Herpes testing is most useful when symptoms are present — blood tests for HSV outside of an active outbreak are less reliable and more complicated to interpret. If you know you’ve had a specific exposure, your provider or testing service can advise on timing.
Q: If I have an STI, do I have to tell my past partners?
Partner notification — informing past sexual partners that they may have been exposed — is strongly recommended and in some cases legally required for certain infections including HIV and syphilis in many US states. Most local and state health departments offer confidential partner notification services that can notify partners without revealing your identity if you’re not comfortable doing so directly. This is an important public health practice that allows partners to get tested and treated.
Q: Are at-home STI tests reliable?
At-home testing kits from reputable services including Everlywell, LetsGetChecked, and myLAB Box are clinically validated and generally reliable for the infections they test for. They are a genuinely useful option for people who prefer privacy or don’t have easy access to a clinic. Important caveats: results should be confirmed by a healthcare provider before initiating treatment, and at-home tests vary in what they include — read carefully what each panel covers.
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for personal health concerns.
References
Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections Prevalence, Incidence, and Cost Estimates. 2021. https://www.cdc.gov/std/statistics/prevalence-2020-at-a-glance.htm
Centers for Disease Control and Prevention (CDC). STI Treatment Guidelines. 2023. https://www.cdc.gov/std/treatment-guidelines/default.htm
Centers for Disease Control and Prevention (CDC). HIV Surveillance Report. 2023. https://www.cdc.gov/hiv/library/reports/hiv-surveillance.html
Centers for Disease Control and Prevention (CDC). HPV Vaccination. 2023. https://www.cdc.gov/hpv/parents/vaccine/index.html
Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1–187. https://pubmed.ncbi.nlm.nih.gov/34292926
Cohen MS, Chen YQ, McCauley M, et al. Antiretroviral therapy for the prevention of HIV-1 transmission. N Engl J Med. 2016;375(9):830–839. https://pubmed.ncbi.nlm.nih.gov/27424812
American Sexual Health Association (ASHA). STI Resource Center. 2023. https://www.ashasexualhealth.org/stdsstis/
