Syphilis is preventable through a combination of barrier protection, regular testing, partner communication, and in some cases, medication taken after exposure. While cases in the U.S. have been declining recently (down 22% from 2023 to 2024, with roughly 41,500 primary and secondary cases reported), the infection rate of about 12 per 100,000 people means prevention still matters, especially for those at higher risk.
Why Syphilis Is Harder to Block Than Some STIs
The bacterium that causes syphilis enters the body through tiny breaks in the skin or through intact mucous membranes, such as those in the mouth, genitals, or rectum. Once it gets in, it moves quickly into deeper tissues and the bloodstream. This matters for prevention because the hallmark sore (called a chancre) can appear anywhere skin-to-skin contact occurs during sex, not just in areas a condom covers. A sore on the base of the penis, the scrotum, the inner thigh, or the vulva sits outside the protection zone of a typical condom.
Syphilis also spreads through oral sex, which many people don’t consider a high-risk activity. If a chancre is present on or around the mouth, or on a partner’s genitals, unprotected oral contact can transmit the infection.
What Condoms Can and Can’t Do
Latex condoms reduce the risk of syphilis transmission when used consistently and correctly, but only when the condom fully covers the infectious sore. Longitudinal studies show a trend toward fewer infections among consistent condom users, though the protection is less complete than it is for infections like HIV or gonorrhea that transmit primarily through fluids rather than skin contact.
This doesn’t mean condoms aren’t worth using. They remain one of the most accessible tools for reducing risk across multiple STIs at once. The key is understanding that condoms lower your chances rather than eliminating them entirely. Dental dams during oral sex provide a similar partial barrier. Using both external and internal condoms for every sexual encounter, including oral sex, adds meaningful protection even if it isn’t perfect.
Doxycycline After Exposure (Doxy-PEP)
In 2024, the CDC released clinical guidelines for using doxycycline as post-exposure prophylaxis, commonly called doxy-PEP. The approach is straightforward: a single 200 mg dose of doxycycline taken as soon as possible within 72 hours after oral, vaginal, or anal sex, with a maximum of 200 mg in any 24-hour period. Clinical trials have shown it significantly reduces the risk of bacterial STIs including syphilis.
Doxy-PEP requires a prescription and a conversation with a healthcare provider about whether it fits your situation. The CDC’s recommendation is built around shared decision-making, meaning your provider discusses the benefits and tradeoffs with you rather than simply handing over a prescription. It’s particularly relevant for men who have sex with men and transgender women who have had a bacterial STI in the past year, the group with the strongest clinical trial evidence behind it.
Testing Is Prevention
Syphilis can be completely painless in its early stages. The initial sore is often firm, round, and doesn’t hurt, which means many people never notice it. Without testing, someone can carry and transmit the infection for months. Regular screening breaks that chain by catching infections early, before they spread to partners or progress to more serious stages.
Current CDC screening recommendations vary by risk level:
- Sexually active men who have sex with men: at least once a year, or every 3 to 6 months if at increased risk
- People living with HIV: at the first HIV evaluation, then at least annually, with more frequent testing based on individual risk
- Pregnant individuals: at the first prenatal visit, with repeat testing at 28 weeks and at delivery for those in high-prevalence areas or with additional risk factors like new partners, multiple partners, or substance use
Testing is a simple blood draw. If you’re sexually active with more than one partner or your partner has other partners, routine syphilis screening is one of the most effective things you can do. Early syphilis is easily curable with antibiotics, but the window for simple treatment narrows as the infection advances.
Screening During Pregnancy
Congenital syphilis, where the infection passes from mother to baby, is almost entirely preventable with timely testing and treatment. The CDC recommends that every pregnant person be screened at the first prenatal visit. For those in communities with high syphilis rates or with risk factors during pregnancy, testing should happen again at 28 weeks and at delivery. No mother or newborn should leave the hospital without the mother’s syphilis status being documented at least once.
Women who arrive at delivery without any prenatal care history, or who had risk factors during pregnancy such as drug use, a new partner, or another STI, should have results from a syphilis test documented before discharge. When syphilis is caught and treated early in pregnancy, transmission to the baby is preventable.
Fewer Partners, Lower Risk
The structure of sexual networks plays a surprisingly large role in how syphilis spreads through a community. Research comparing outbreak and non-outbreak areas found that in places without outbreaks, people with fewer partners tended to pair with other low-risk individuals, forming a natural barrier against widespread transmission. In outbreak settings, frequent crossover between people with many partners and those with fewer partners created bridges that carried the infection into otherwise low-risk groups.
In practical terms, reducing your number of sexual partners lowers your exposure to these transmission chains. A mutually monogamous relationship where both partners have tested negative is the lowest-risk scenario. If you have multiple partners, the other strategies here (condoms, testing, doxy-PEP, open communication) become more important to layer together.
Telling Partners Matters More Than You Think
When someone is diagnosed with syphilis, notifying their recent sexual partners is one of the most effective ways to stop the infection from cycling back or spreading further. A study spanning over a decade in Georgia found that when partners couldn’t be located or notified, the diagnosed person was 40% more likely to be reinfected with syphilis within two years compared to those whose partners were all reached and treated.
You can notify partners yourself or, in most areas, ask your local health department to do it confidentially without revealing your name. Many health departments have dedicated partner services staff trained in exactly this process. The goal isn’t blame. It’s making sure exposed people get tested and treated before they unknowingly pass the infection along.
Layering Strategies Together
No single prevention method is foolproof for syphilis. Condoms help but don’t cover all potential exposure sites. Testing catches infections but only after they’ve occurred. Doxy-PEP is promising but requires timely access and a prescription. The most effective approach combines several of these tools based on your own level of risk.
Someone in a long-term monogamous relationship where both partners tested negative at the start may not need anything beyond occasional screening. Someone with multiple partners might combine consistent condom use, testing every 3 to 6 months, and a doxy-PEP prescription for higher-risk encounters. The right combination depends on your circumstances, and it can change over time as your situation changes.