Syphilis is everywhere. How it spreads and why early treatment matters.

Syphilis is everywhere. How it spreads and why early treatment matters.

Daryl Austin, USA TODAY

Wed, December 17, 2025 at 10:02 AM UTC

4 min read

If “syphilis” sounds to you like an illness people got in another century, you’re not alone. For decades, the infection was widely considered a disease of the past. But after years of decline, syphilis is quietly making a comeback, with rates now higher than at any time since the 1950s.

And here’s the tricky part: Someone might not even realize they have it. That's because its symptoms can resemble many unrelated conditions, and the disease “develops in stages,” says Dr. Orchideh Alexander, an obstetrics and gynecology physician with Atlantic Health in New Jersey.

Here's what syphilis is, how to recognize it, how it spreads and why timely treatment can cure it fully.

What is syphilis? What does syphilis look like?

Syphilis is a sexually transmitted infection caused by the corkscrew-shaped bacterium Treponema pallidum, says Dr. Krystal Green, a primary care physician with Inspira Health in New Jersey. Although it is less common than sexually transmitted infections like chlamydia or gonorrhea, it remains alarmingly prevalent. Data from the World Health Organization estimate that 8 million people worldwide between ages 15 and 49 contracted syphilis in 2022.

Symptoms depend on the stage of the disease. Primary syphilis is the first stage, and usually begins with a single sore called a chancre. This “can be either a painless or painful nodule which then becomes an open sore or ulcer,” Green explains. While typically found on the genitals, chancres can also appear in the throat or anus. Because the sore heals within three to six weeks – even without treatment – many people overlook it.

If untreated, the infection progresses to secondary syphilis about four to 10 weeks later. This stage may cause fever, chills, swollen lymph nodes, malaise, headaches, muscle aches and sometimes “hair loss, abdominal pain or joint swelling,” says Dr. Michael Shen, an internal medicine physician at NYC Health + Hospitals/Brooklyn. But he says the hallmark symptom "is a distinctive rash" known for being faint, non-itchy reddish-brown spots, often on the palms of the hand and soles of the feet.

After this, the infection may enter a latent stage, during which it causes no symptoms but remains active in the body for years. Without treatment, some people eventually develop tertiary syphilis, which Alexander says can damage the heart, brain and nervous system. “Tertiary syphilis can develop anytime from one to 30 years after primary infection,” adds Green.

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How do you get syphilis?

Syphilis spreads primarily through vaginal, anal or oral sex, Shen explains. Condoms greatly reduce risk, but they do not fully eliminate it because the bacteria can still enter through tiny breaks in the skin or mucous membranes that lie outside the area a condom covers.

In fact, Green explains that because these sores are so infectious – even if they’re small, painless or hidden – the disease can also spread through non-sexual contact, including by "touching a person with open, active lesions on their body."

The disease can also be "maternally transmitted from mother to fetus in utero," she adds.

Noted: Have you been told you're allergic to penicillin? Here's why you're probably not.

How is syphilis treated? Is syphilis curable?

The good news is that "syphilis is a completely treatable sexually transmitted infection no matter which stage it is diagnosed in,” Green explains. “However, damage to the nervous system, heart and other organs in late-stage syphilis may be irreversible.”

The standard treatment is a single injection of long-acting benzathine penicillin G, but "for later stages, you may have to receive multiple injections over several weeks,” Shen notes. People with penicillin allergies also have the option of being treated with alternatives such as doxycycline.

After treatment, follow-up blood tests confirm that the infection has cleared. Your doctor can also screen for other STIs and recommend prevention strategies such as consistent condom use, open communication about sexual health and regular STI testing. They may also mention "doxy PEP" – taking doxycycline within 72 hours of having sex to try and prevent syphilis and other STIs – something the Centers for Disease Control and Prevention recommends medical providers mention to gay and bisexual men and transgender women who, within the last year, had chlamydia, syphilis or gonorrhea.

Doctors also help their patients understand the importance of timing. “The earlier syphilis is treated,” Alexander says, “the easier it is to cure and the less long-term harm it causes.”

This article originally appeared on USA TODAY: What is syphilis? What does syphilis look like?

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