Dec. 17, 2025, 5:02 a.m. ET
if “syphilis” sounds 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 as 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. Even though it is indeed less common than sexually transmitted infections like chlamydia or gonorrhea, it remains alarmingly prevalent. Data from the World Health institution estimate that 8 million people worldwide between ages 15 and 49 contracted syphilis in 2022.
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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 distinct