STIs Overview: Chlamydia, Gonorrhea, and Syphilis Management

Chlamydia, gonorrhea, and syphilis are the most common bacterial sexually transmitted infections (STIs) in the U.S. and globally. Together, they accounted for over 2.5 million cases in 2021, with half of those infections happening in people between 15 and 24 years old. These infections don’t always cause symptoms, which is why they spread so easily-and why they can cause serious, long-term damage if left untreated.

What You Need to Know About Chlamydia

Chlamydia, caused by the bacteria Chlamydia trachomatis, is the most frequently reported bacterial STI in the United States. About 70% of infected women and half of infected men show no symptoms at all. When symptoms do appear, they might include abnormal vaginal discharge, burning during urination, or pain during sex. In men, it can cause swelling or pain in the testicles.

Left untreated, chlamydia can lead to pelvic inflammatory disease (PID) in up to 15% of women. PID scars the fallopian tubes, which can result in infertility or ectopic pregnancy-a life-threatening condition where the embryo implants outside the uterus. Chlamydia also increases the risk of getting HIV by two to three times because it causes inflammation in the genital lining.

The standard treatment is a single dose of azithromycin (1 gram) or a week-long course of doxycycline (100 mg twice daily). Both are over 95% effective when taken correctly. But reinfection is common: 14 to 20% of young women test positive again within a year. That’s why the CDC recommends retesting three months after treatment, even if your partner was treated.

Gonorrhea: A Growing Threat

Gonorrhea, caused by Neisseria gonorrhoeae, is the second most common bacterial STI. Like chlamydia, it often has no symptoms-especially in women. When symptoms do show up, they include thick yellow or green discharge, painful urination, and bleeding between periods. Rectal infections can cause itching, discharge, or pain during bowel movements.

The real danger with gonorrhea isn’t just its ability to cause PID and infertility-it’s antibiotic resistance. The CDC now classifies gonorrhea as an “urgent threat” because the bacteria have become resistant to nearly every antibiotic ever used to treat it. In some areas, up to half of gonorrhea strains are already resistant to azithromycin, one of the two drugs used in current treatment.

Current CDC guidelines require a dual therapy approach: a single 500 mg injection of ceftriaxone plus a single 1-gram oral dose of azithromycin. Even this combo isn’t foolproof. Pharyngeal (throat) infections have higher failure rates, so a follow-up test is needed 7 to 14 days after treatment. If you’ve had unprotected oral sex, don’t assume you’re in the clear.

There’s hope on the horizon: a new drug called zoliflodacin showed 96% effectiveness in Phase 3 trials and could be approved by the FDA in 2025. Until then, prevention and early testing are your best defenses.

Syphilis: The Silent Resurgence

Syphilis, caused by Treponema pallidum, is the most complex of the three. It doesn’t just disappear after treatment-it can hide in your body for years and come back with devastating consequences.

The infection moves in stages. The first sign is a painless sore (chancre) at the site of infection-usually on the genitals, anus, or mouth. It heals on its own, so many people don’t realize they’re infected. Weeks later, a rash may appear on the palms and soles, along with fever, swollen lymph nodes, and fatigue. This is the secondary stage. If untreated, syphilis can enter a latent phase, where there are no symptoms for years. Then, decades later, it can attack the heart, brain, and nervous system, causing stroke, dementia, or blindness.

What’s alarming is the recent surge in congenital syphilis-babies born infected. Between 2017 and 2021, cases jumped by 273%. The CDC now recommends that all pregnant women be tested at their first prenatal visit, and again at 28 weeks in areas with high rates. Untreated syphilis during pregnancy can cause stillbirth, premature birth, or severe birth defects.

Treatment is straightforward but depends on the stage. Early syphilis (within the first year) is cured with one shot of benzathine penicillin G (2.4 million units). Late syphilis requires three weekly shots. There’s no alternative to penicillin for pregnant women-other antibiotics won’t protect the baby.

Testing, Partner Notification, and Retesting

Testing is the first step to stopping the spread. Chlamydia and gonorrhea are usually detected with a urine sample or a swab from the genitals or throat. Syphilis requires a blood test. Many clinics offer rapid testing with results in under an hour.

If you test positive, your sexual partners from the last 60 days (for chlamydia and gonorrhea) or up to 90 days (for syphilis) need to be tested and treated-even if they feel fine. This is called partner notification. Many health departments offer anonymous partner notification services to protect your privacy.

Retesting is non-negotiable. For chlamydia and gonorrhea, get tested again three months after treatment. For syphilis, blood tests are repeated at 6 and 12 months to confirm the infection is gone. Don’t skip this step. Reinfection is common, and each new infection increases your risk of complications.

Prevention: Beyond Condoms

Condoms reduce transmission by 60-90% for chlamydia and gonorrhea, and 50-70% for syphilis. But they’re not perfect, especially for infections spread through skin-to-skin contact like syphilis sores.

A newer tool is doxycycline post-exposure prophylaxis, or DoxyPEP. Taking a single 200 mg dose of doxycycline within 72 hours after unprotected sex can cut the risk of chlamydia, gonorrhea, and syphilis by up to 73%-but only for men who have sex with men and transgender women on PrEP. Studies in cisgender women didn’t show the same benefit, so it’s not recommended for them.

The CDC only supports DoxyPEP for high-risk groups because of concerns about antibiotic resistance. It’s not a substitute for regular testing or consistent condom use.

Why This Matters Beyond Your Health

These infections don’t just affect individuals-they strain the entire healthcare system. In the U.S., the annual cost of treating STIs exceeds $16 billion. Chlamydia alone accounts for about $500 million in direct medical costs. Racial disparities are stark: Black Americans have chlamydia rates 5.6 times higher, gonorrhea rates 6.7 times higher, and syphilis rates 3.5 times higher than White Americans.

These gaps aren’t about behavior-they’re about access. People in underserved communities face barriers to testing, treatment, and education. The WHO’s Global STI Strategy 2021-2030 aims to cut syphilis in pregnant women by 90% and reduce chlamydia and gonorrhea by 70%. But without better access to care, those goals won’t be met.

There’s a reason experts call chlamydia a “silent epidemic” and syphilis a “resurgence.” They’re not going away. They’re getting harder to treat. And they’re spreading fastest among the people who need help the most.

What You Can Do Today

• Get tested annually if you’re sexually active-more often if you have new or multiple partners.
• Use condoms every time you have vaginal, anal, or oral sex.
• Ask partners about their STI status and testing history.
• If you test positive, tell your partners and get retested in three months.
• Don’t ignore symptoms like discharge, pain, or rashes-even if they go away.
• Ask your provider about DoxyPEP if you’re a high-risk MSM or transgender woman on PrEP.

These infections are treatable. But they’re not harmless. The best way to protect yourself and others is to know the signs, get tested regularly, and never assume you’re safe just because you feel fine.