Understanding Syphilis: How the Infection Progresses Through Its Stages
Syphilis is one of the oldest known sexually transmitted infections, yet it remains a significant public health concern today. According to the Centers for Disease Control and Prevention (CDC), reported syphilis cases in the United States have been rising steadily, with over 207,000 cases reported in 2022 alone — the highest number recorded in more than 70 years. Understanding how syphilis behaves in the body is one of the most important steps toward recognizing it, treating it, and protecting both yourself and your partners.
What makes syphilis particularly tricky is that its symptoms change dramatically over time — and sometimes disappear entirely, creating a false sense of security. Syphilis progresses through distinct stages, each with its own set of signs. Here's what you need to know about each one.
What Causes Syphilis?
Syphilis is caused by a bacterium called Treponema pallidum. It spreads through direct contact with a syphilitic sore (called a chancre) during vaginal, anal, or oral sex. It can also be passed from a pregnant person to their baby during pregnancy or childbirth, which is known as congenital syphilis. Importantly, syphilis cannot be spread through casual contact like sharing toilets, doorknobs, or clothing.
Stage 1: Primary Syphilis
The first stage of syphilis typically begins 10 to 90 days after exposure, with an average onset of about 21 days. The hallmark symptom of primary syphilis is the appearance of a chancre — a small, round, firm sore that is usually painless.
What does the chancre look like?
- It is typically round, firm, and painless (though some can be tender)
- It appears at the site where Treponema pallidum entered the body
- Common locations include the penis, vagina, anus, rectum, lips, or mouth
- It usually heals on its own within 3 to 6 weeks
Because the sore is often painless and may appear in a hidden location (inside the vagina, rectum, or under the foreskin), many people never notice it. This is one of the main reasons syphilis so often goes undetected and untreated in its earliest — and most treatable — stage.
Stage 2: Secondary Syphilis
If primary syphilis is not treated, the infection advances to the secondary stage, usually a few weeks after the chancre heals. This stage is characterized by more widespread symptoms as the bacteria spread throughout the body via the bloodstream.
Common symptoms of secondary syphilis include:
- Skin rash — often appearing on the palms of the hands and soles of the feet, though it can cover the whole body. The rash is usually rough, red, or reddish-brown in color.
- Mucous membrane lesions — sores in the mouth, vagina, or anus
- Flu-like symptoms such as fever, fatigue, and sore throat
- Swollen lymph nodes
- Hair loss in patches (called alopecia)
- Headaches and muscle aches
- Condyloma lata — flat, wart-like growths in warm, moist areas of the body
Like primary symptoms, the signs of secondary syphilis will go away on their own without treatment. However, this does not mean the infection is gone — it simply moves into the next phase. The disappearance of symptoms can make people believe they have recovered, which is a dangerous misconception.
The Latent Stage: When Syphilis Hides
After secondary symptoms fade, syphilis enters a latent (hidden) stage in which there are no visible symptoms at all. This stage is divided into two periods:
- Early latent syphilis: Infection within the past 12 months. The person may still be infectious.
- Late latent syphilis: Infection lasting more than 12 months. The person is generally less infectious to sexual partners, but the bacteria remain in the body.
The latent stage can last for years or even decades. Without testing, a person in the latent stage would have no way of knowing they are infected. This is why routine syphilis testing is so critically important, especially for sexually active individuals with multiple partners.
Stage 3: Tertiary (Late) Syphilis
Without treatment, approximately 15 to 30% of people with untreated syphilis will develop tertiary syphilis, according to the CDC. This stage can occur 10 to 30 years after the initial infection and represents the most severe and potentially life-threatening phase of the disease.
Tertiary syphilis can affect multiple organ systems, including:
- The heart and blood vessels (cardiovascular syphilis) — causing aortic aneurysms and other serious complications
- The brain and nervous system (neurosyphilis) — leading to memory problems, personality changes, blindness, deafness, meningitis, or dementia
- Gummas — soft, tumor-like growths that can form in the skin, bones, liver, and other organs
Tertiary syphilis is now relatively rare in countries with access to healthcare and routine screening, but it remains a serious risk for those who go undiagnosed or untreated. Neurosyphilis, in particular, can develop at any stage of syphilis, not just the tertiary stage, making early detection even more important.
Congenital Syphilis: A Risk to Newborns
It's worth noting that syphilis can be passed from a pregnant person to their baby. Congenital syphilis can cause stillbirth, premature birth, low birth weight, or serious health problems in newborns. The CDC reported a staggering 3,761 cases of congenital syphilis in 2022, underlining the urgent need for prenatal syphilis screening.
The Good News: Syphilis Is Curable
Despite its potentially serious consequences, syphilis is completely curable with antibiotics, particularly penicillin. When caught early — in the primary or secondary stage — treatment is straightforward and highly effective. Even in later stages, treatment can stop further damage, though it cannot reverse harm that has already occurred.
This is why early detection through regular testing is so powerful. A simple blood test is all it takes to know your status.
Take Control of Your Sexual Health: Get Tested Today
If you are sexually active, getting tested for syphilis is one of the most responsible and caring things you can do — for yourself and for your partners. Testing is quick, confidential, and widely available at your primary care doctor's office, sexual health clinics, Planned Parenthood locations, and through at-home testing kits.
The CDC recommends that all sexually active gay and bisexual men be tested for syphilis at least once a year, and that all pregnant people be tested at their first prenatal visit. Anyone with new or multiple sexual partners should also consider routine testing.
Don't wait for symptoms to appear — because with syphilis, they often don't. Knowing your status gives you the power to protect your health and the health of those you care about. Reach out to a healthcare provider or visit a local clinic today. You deserve to feel informed, empowered, and cared for.