Syphilis is one of the most common reportable infectious diseases in the United States.¹ It tends to be most common in large metropolitan cities.

Since the discovery of the antibiotic penicillin, the incidence of syphilis in the general population has dropped, as have many other infectious diseases. But after hitting an all-time low in 2000, the rate of syphilis infection has been going up.²

• Syphilis is most common in sexually active people 15 to 30 years of age. This age range is considered a more sexually active period for most people.³
• About 6 out of 10 syphilis infections affect men who have sex with men.²
• The syphilis rate seems to be increasing among men and women who have heterosexual sex.²
• There has been a rise in the number of people who have both syphilis and the human immunodeficiency virus (HIV). This is especially the case among men who have sex with men.²

Open syphilis sores provide easy access to transmit or receive HIV infection during sexual intercourse. This may be particularly important in those parts of the country, such as the southern half of the United States, where rates of both infections are high.

Syphilis without another sexually transmitted disease is now more commonly seen in adults older than 30 years of age.