What is syphilis?

Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. primary and secondary (P&S) syphilis is the earliest and most transmissible stages of syphilis.  Syphilis can cause serious health problems if not adequately treated. The nation is facing an increase in syphilis rates among both men and women in every region of the country, especially in gay and bisexual men.


How common is syphilis?

In 2018, there were 115,045 new diagnoses of syphilis compared to about 38,739 of HIV infection and 583,405 of gonorrhea. Of the syphilis cases, 35,063 were P&S syphilis. The majority of the cases occurred among gay, bisexual, and other men who have sex with men (MSM).  MSM accounted for 77.6% of all P&S syphilis cases among males in which sex of sex partner was known and 64.3% of P&S syphilis cases among men or women with information about sex of sex partner. However, in recent years, the rate of P&S syphilis has been increasing among MSM as well as heterosexual men and women.

Syphilis and HIV

In the United States, approximately half of men who have sex with men (MSM) with syphilis were also living with HIV. MSM who are HIV-negative and diagnosed with P&S syphilis are more likely to be infected with HIV in the future. Genital sores caused by syphilis also make it easier to transmit and acquire HIV infection sexually.



Correct and consistent use of latex condoms can reduce the risk of syphilis when the infected area or site of potential exposure is protected. However, a syphilis sore outside of the area covered by a latex condom can still allow transmission.

Because chancres can be hidden in the vagina, rectum, or mouth, it may not be obvious that a sex partner has syphilis. Unless a person knows that their sex partners have been tested and treated, they may be at risk of being infected or re-infected by an untreated partner


The best 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 known to be uninfected.

Partner-based interventions include partner notification, is a critical component in preventing the spread of syphilis. Sexual partners of infected patients should be considered at risk and provided treatment immediately


The definitive method for diagnosing syphilis is visualizing the Treponema pallidum bacterium via darkfield microscopy. Home self-tests kits are also available but not often reliable. These tests are simple, inexpensive, and are often used for screening.


Who should be tested for syphilis?

Any person with signs or symptoms suggestive of syphilis should be tested for syphilis. Also, anyone with an oral, anal, or vaginal sex partner who has been recently diagnosed with syphilis should be tested for syphilis.

Routine testing is recommended for those who

  • are pregnant;
  • are sexually active men who have sex with men (MSM);
  • are living with HIV and are sexually active;
  • are taking PrEP for HIV prevention.



Transmission of syphilis can occur during vaginal, anal, or oral sex, by direct contact with a syphilitic sore, known as a chancre. These chancres can appear on or around the external genitals, in the vagina, around the anus, the rectum, or in or around the mouth. Pregnant women with syphilis can transmit the infection to their unborn child.

Signs and Symptoms

Syphilis is known as “The Great Pretender”, as its symptoms mimics many other diseases. Syphilis typically follows stages that can last for weeks, months, or even years Symptoms appearance can range from 10 to 90 days, but the average time between acquisition of syphilis and the first symptom is about 21 days.


Primary Stage

The appearance of a single chancre marks the primary (first) stage of syphilis symptoms, but there may be multiple sores. The chancre is usually firm, round, and painless. It appears at the location where syphilis entered the body. These painless chancres can occur in locations that make them difficult to notice (e.g., the vagina or anus). The chancre lasts 3 to 6 weeks and heals regardless of whether a person is treated or not. However, if the infected person does not receive adequate treatment, the infection progresses to the secondary stage.

Secondary Stage