Without treatment, syphilis lasts a lifetime. The bacteria never clear on their own, and the infection moves through distinct stages over years or even decades. With treatment, syphilis can be cured relatively quickly, and you’re typically no longer infectious within about a week of starting antibiotics.
How Long Each Stage Lasts Without Treatment
Syphilis progresses through four stages, each with its own timeline. The first sign is usually a painless sore called a chancre, which appears at the site of infection roughly 3 weeks after exposure (though it can show up anywhere from 10 to 90 days later). This sore heals on its own within 3 to 6 weeks, which leads many people to assume the infection has gone away. It hasn’t.
The secondary stage begins weeks to a few months after the chancre heals. This is when you might notice a rash (often on the palms or soles of the feet), fever, swollen lymph nodes, sore throat, or patchy hair loss. These symptoms also resolve on their own, typically within a few weeks to months. Again, the infection is still active in your body.
After the secondary stage, syphilis enters a latent (hidden) phase where there are no visible symptoms at all. This stage can last years or even the rest of your life. Most people with untreated syphilis stay in this latent phase permanently. But roughly 15 to 30 percent of untreated people eventually develop tertiary syphilis, the most dangerous stage, which appears 10 to 30 years after the original infection.
When Syphilis Becomes Dangerous
Tertiary syphilis can damage the heart, blood vessels, brain, bones, and other organs. By this point, the infection has been silently present in the body for a decade or more. Some people develop large inflammatory masses called gummas in soft tissue or bone. Others develop cardiovascular problems, including damage to the aorta.
The bacteria can also invade the nervous system at any point during the infection, not just in the late stages. Early neurological involvement, which can appear within weeks to years of the initial infection, may cause headaches, neck stiffness, and nausea. A more serious form involving the blood vessels of the brain typically shows up 5 to 10 years after infection and can cause stroke-like symptoms. The latest forms of nervous system involvement are the most severe: one causes cognitive decline, personality changes, and mood disturbances 15 to 20 years post-infection, while another affects the spinal cord and can appear anywhere from 5 to 50 years later, causing problems with balance, bladder control, and sharp shooting pains.
How Long You’re Contagious
Syphilis is most contagious during the primary and secondary stages, when sores or rashes are present. It can also spread during the early latent phase (the first year or so after infection). After that first year, transmission to sexual partners becomes much less likely, though the infection can still be passed from a pregnant person to their baby at any stage.
The contagious window without treatment can stretch across months to a couple of years. With treatment, the window closes much faster. Current guidelines recommend avoiding sexual contact for at least 7 days after treatment begins or until symptoms have fully resolved, whichever takes longer.
How Quickly Treatment Works
Syphilis is cured with antibiotics, and for early-stage infections, a single injection is often all that’s needed. The bacteria are killed relatively quickly, but your body takes longer to show evidence of recovery on blood tests.
After successful treatment for primary syphilis, standard blood tests (the kind that measure your body’s immune response to the infection) should show a meaningful decline within 6 months. For early latent syphilis, that same decline takes up to 12 months. If you were treated during a later stage, the drop can take even longer, and some people’s test results never fully return to zero.
This is an important detail that catches many people off guard: one type of syphilis blood test will likely stay positive for the rest of your life, even after successful treatment. These tests detect antibodies your immune system made in response to the bacteria, and those antibodies persist indefinitely in most cases. The only notable exception is people treated very early, during the primary stage. About 15 to 25 percent of them will test negative on these antibody tests within 2 to 3 years. For anyone treated at a later stage, the positive result is essentially permanent. A positive result on this type of test does not mean you still have syphilis. It means you had it at some point.
Early Treatment vs. Late Treatment
The stage at which you’re treated makes a significant difference in outcomes. Early treatment (during the primary, secondary, or early latent stages) cures the infection and prevents any long-term damage. The body heals fully, and the only lasting trace is likely a positive antibody test.
Treatment during the late latent or tertiary stages still kills the bacteria, but it cannot reverse damage that has already occurred. If syphilis has affected the heart, brain, or nervous system, those changes may be permanent even after the infection itself is gone. This is why timing matters so much. The infection is easiest to cure and least harmful when caught in its first year or two, but it can persist silently for decades if no one is looking for it.