Syphilis and Men Who Have Sex With Men

Medically Reviewed by Traci C. Johnson, MD on March 09, 2024
6 min read

Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. It has often been called "the great imitator," because so many of the signs and symptoms of syphilis are indistinguishable from those of other diseases.

The syphilis bacterium is passed from person to person through direct contact with a syphilis sore (also called a chancre). Sores occur mainly on the external genitals, in the vagina, on the anus, and in the rectum. Sores also can occur on the lips and in the mouth (areas covered by mucous membranes). Transmission of the bacterium occurs during vaginal, anal, or oral sex. Persons with either primary or secondary syphilis (in the early stages) can transmit the disease. Pregnant women with the disease can pass it to the babies they are carrying. Syphilis cannot be spread through casual contact, such as with toilet seats, door knobs, swimming pools, hot tubs, bath tubs, shared clothing, or eating utensils.

Over the past several years, increases in syphilis among men who have sex with other men have been reported. In the recent outbreaks, 20% to 70% of cases occurred in men who also have HIV. While the health problems caused by syphilis in adults are serious in their own right, it is now known that the genital sores caused by syphilis in adults also make it easier to transmit and acquire HIV infection sexually. In fact, there is a two- to five-fold increased risk of acquiring HIV infection when syphilis is present.

Primary Stage

The primary stage of syphilis is usually marked by the appearance of a single sore, but there may be multiple sores. The duration between infection with syphilis and the onset of the first symptoms can range from 10-90 days (average 21 days). The sore begins as a pimple, but quickly ulcerates to form a firm, round, small, and painless ulcer. If it is inside the vagina or anus, it is easy to miss this stage.It appears at the spot where the syphilis bacterium entered the body. The sore generally lasts three to six weeks, and it heals with or without treatment. However, if adequate treatment is not administered, the infection can progress to secondary syphilis. At this stage, people are highly infectious.

Secondary Stage

The secondary stage of syphilis is characterized by a skin rash and mucous membrane sores. This stage typically starts with the development of a rash on one or more areas of the body -- the rash usually does not cause itching. Rashes associated with secondary syphilis can appear as the initial sore is healing or several weeks after it has healed. The characteristic rash of secondary syphilis may appear as rough, red, or reddish-brown spots both on the palms of the hands and the bottoms of the feet. However, rashes with a different appearance may occur on other parts of the body, sometimes resembling rashes caused by other diseases. Sometimes rashes associated with secondary syphilis are so faint that they are not noticed. In addition to rashes, symptoms of secondary syphilis may include fever, swollen lymph glands, sore throat, patchy hair loss, headaches, weight loss, muscle aches, and fatigue. The signs and symptoms of secondary syphilis will resolve with or without treatment, but without treatment, the infection may progress to the latent and late stages of disease.

Late Stage

The latent (hidden) stage of syphilis begins when secondary symptoms disappear. Without treatment, the infection remains in the body. In the late stages of syphilis, the internal organs, including the brain, nerves, eyes, heart, blood vessels, liver, bones, and joints may subsequently be damaged. This internal damage may show up many years later. Signs and symptoms of the late stage of syphilis include difficulty coordinating muscle movements, paralysis, numbness, gradual blindness, and dementia. This damage may be serious enough to cause death.

Two different blood tests are needed to determine whether someone has syphilis. Shortly after infection occurs, the body produces antibodies against syphilis that can be detected by an accurate, safe, and inexpensive blood test. A low level of antibodies will remain in the blood for months or years, even after the disease has been successfully treated.

The genital sores (ulcers) caused by syphilis make it easier to transmit and acquire HIV infection sexually.

Sexually transmitted diseases (STDs) that cause sores, such as syphilis, disrupt barriers that provide protection against infections. The genital ulcers caused by syphilis can bleed easily, and when they come into contact with oral and rectal mucous membranes during sex, they increase the infectiousness of, and susceptibility to, HIV. Having other STDs is also an important predictor for becoming HIV-infected, because STDs are a marker for behaviors associated with HIV transmission.

Syphilis is easy to cure in its early stages. A single injection of penicillin, an antibiotic, will cure a person who has had syphilis for less than a year. Additional doses are needed to treat someone who has had syphilis for longer than a year. For people who are allergic to penicillin, other antibiotics are available to treat syphilis. Treatment will kill the syphilis bacterium and prevent further damage, but it will not repair damage already done. There are no home remedies or over-the-counter drugs that will cure syphilis.

Because effective treatment is available and infection isn't always obvious, it is important that people be screened for syphilis on an on-going basis if their sexual behaviors put them at risk for STDs.

Persons who receive syphilis treatment must abstain from sexual contact with new partners until the syphilis sores are completely healed. Persons with syphilis must notify their sex partners so that they also can be tested and receive treatment.

Having syphilis once does not protect a person from getting it again. Following successful treatment, people can still be susceptible to re-infection. Only lab tests can confirm whether someone has syphilis. Because syphilis sores can be hidden in the vagina, rectum, or mouth, it may not be obvious that a sex partner has syphilis. Talking with your health care provider will help you determine if you need to get re-tested for syphilis after you have received treatment.

The surest way to avoid transmission of sexually transmitted diseases, including syphilis, is to abstain from sexual contact or to be in a long-term mutually monogamous relationship with a partner who has been tested and is not infected.

Avoiding alcohol and drug use may also help prevent transmission of syphilis, because these activities may lead to risky sexual behavior. It is important that sex partners talk to each other about their HIV status and history of other STDs so that preventive action can be taken.

For persons whose sexual behaviors place them at risk for STDs, correct and consistent use of male condoms (and dental dams during oral sex) can help reduce the risk of syphilis transmission. However, genital ulcer diseases like syphilis are transmitted primarily through "skin-to-skin" or "surface-to-surface" contact from sores that may not be covered by condoms. Correct and consistent use of male latex condoms can reduce the risk of transmission only if infected areas or sites of potential infection are covered.

Condoms lubricated with spermicides containing Nonoxynol-9 or N-9 are no more effective than other lubricated condoms in protecting against the transmission of STDs. Based on findings from several research studies, N-9 may itself cause genital lesions, providing a point of entry for HIV and other STDs. The CDC recommends that N-9 not be used as a microbicide or lubricant during anal intercourse.

Washing the genitals, urinating, and/or douching after sex does not prevent STDs, including syphilis. Any unusual discharge, sore, or rash, particularly in the groin area, should be a signal to refrain from having sex and to see a doctor immediately.