The incidence of syphilis has been increasing rapidly in the US; from 2015 to 2020, the primary and secondary syphilis rate among women increased 147% (from 1.9 to 4.7 per 100, 000), and the rate among men increased 34% (from 15.5 to 20.8 per 100, 000) (see Centers for Disease Control and Prevention Preliminary 2021 STD Surveillance Data and Sexually Transmitted Disease Surveillance 2020: Syphilis).