Vivien Williams: Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Dr. Stacey Rizza, an infectious diseases specialist at Mayo Clinic, says syphilis affects men and women and can present in various stages.

Stacey Rizza, M.D.: Primary syphilis causes an ulcer, and this sometimes isn't noticed because it's painless and can be inside the vagina or on the cervix…after a few weeks, two months, they can get secondary syphilis, which is a rash.

Vivien Williams: It may then progress to latent stage syphilis and, finally, the most serious stage: tertiary. Pregnant women are not immune to syphilis. Congenital syphilis can lead to miscarriage, stillbirth or infant deaths. That's why all pregnant women should be screened. Syphilis is preventable and treatable. As for prevention, Dr. Rizza recommends barrier protection during sex.

Dr. Rizza: And that's during oral sex, anal sex, vaginal sex — using condoms, dental dams and any other barrier protection.

Vivien Williams: For the Mayo Clinic News Network, I'm Vivien Williams.