Syphilis is a sexually transmitted infection caused by Treponema pallidum bacteria. It can be cured with antibiotics, but if left untreated, it can cause severe complications, including heart damage and neurological problems.

Gay and bisexual men have the highest rate of syphilis, but it is increasing among heterosexual men and women, and congenital syphilis in newborns is on the rise. HIV-positive people with syphilis lesions are more likely to transmit HIV, and HIV-negative people with syphilis sores are more likely to acquire the virus. People living with HIV—especially those with a low CD4 count—may develop more severe syphilis and may not respond as well to treatment.

Syphilis has been dubbed “the great imitator” because its symptoms can resemble those of many other conditions.

Primary syphilis typically starts as a painless sore known as a chancre. These appear most often on the penis, vulva, vagina, anus or mouth—the sites where the bacteria enter the body. The initial sore usually heals without treatment, but the person remains infected.

Secondary syphilis usually develops within several weeks after the initial chancre has healed. The most common symptom is pox-like lesions that can appear anywhere on the body, including the palms of the hands and soles of the feet. Other symptoms may include fever, swollen lymph nodes, sore throat, fatigue, hair loss, headache and muscle aches. Symptoms typically resolve within several weeks, but the bacteria remain in the body.

Latent syphilis is an asymptomatic stage that can last for years. People with latent syphilis are less likely to transmit the bacteria, but treatment is recommended to prevent serious late-stage complications.

Tertiary syphilis occurs in up to one third of people who remain untreated, usually 10 to 30 years after initial infection. The bacteria can damage organs throughout the body, including the brain, nerves, eyes, ears, heart, blood vessels, liver, bones and joints.

Neurosyphilis occurs when the bacteria infect the nervous system. Neurosyphilis, ocular syphilis (affecting the eyes) and otosyphilis (affecting the ears) can occur at any stage of infection. Neurological damage may lead to numbness, paralysis, blindness, deafness, cognitive impairment and dementia.


Congenital syphilis occurs when a mother passes the bacteria to her baby during pregnancy or delivery. Congenital syphilis can cause miscarriages, stillbirth and premature birth. Many infants don’t have any symptoms at birth, but if left untreated, they can develop serious complications including bone or teeth deformities, neurological problems, blindness and deafness.

Syphilis is usually passed from person to person through direct contact with active sores during vaginal, anal or oral sex. The bacteria are present in semen and vaginal fluid. It’s important to avoid contact with sores during sex and to avoid having sex if you have active lesions. Condoms can reduce the risk, but they’re not fully protective because sores can occur in areas not covered by a condom. Recent research shows that taking doxycycline as post-exposure prophylaxis after sex—known as doxy PEP—reduces the risk for syphilis in people at high risk.

Get tested if you have symptoms suggestive of syphilis or if a sex partner has tested positive. The Centers for Disease Control and Prevention recommends regular testing—even if asymptomatic—for sexually active gay and bisexual men, people with HIV and those using HIV pre-exposure prophylaxis (PrEP). Pregnant people should
be tested during their first prenatal visit.

Syphilis can be treated at any stage. The standard treatment is injectable benzathine penicillin. A single injection in the buttocks is usually enough to treat primary or secondary syphilis. People with late-stage syphilis should receive weekly penicillin injections for three weeks. Neurosyphilis and eye and ear manifestations require more intensive treatment. Follow-up blood tests should be done after treatment to make sure it was successful. And remember: Syphilis does not confer immunity, so it is possible to get it again.