It's a sexually-transmitted infection caused by the Treponema pallidum bacteria. The infection causes small sores, and contact with these sores is the primary way by which the infection spreads. That bacteria can then enter your system in a bunch of different ways, including via small cuts on your skin or through a mucus membrane, such as your vagina. The CDC also notes that pregnant women can spread the infection to their fetuses , which can cause stillbirth. In some rare cases, a person with syphilis sores in their mouth may spread the bacteria to someone else while kissing. But it's important to remember that you cannot get it by sharing utensils, bathtubs, doorknobs, that kind of thing, with someone who is infected — it's not like catching a cold.The symptoms of syphilis show up in a few distinct stages, explains the CDC . At first, you'll develop a few small, painless sores on the part of your body where you were initially exposed to the bacteria. Some people only have one barely-noticeable sore at this stage. In the second stage, you'll develop a rash. That might start with wart-like bumps around your genitals, but then it might show up on other areas of your body (including your hands and feet) as rough, red or reddish brown spots. The rash won't itch and may be so faint you don't even notice it. But you may also have flu- or cold-like symptoms, including a sore throat, swollen lymph nodes, fever, muscle aches, headache, and fatigue. The symptoms of the first two stages will go away on their own. But if you don't get treatment, the infection can stay latent in your body for decades. Most people don't have symptoms later on, but up to 30% of people go on to develop late-stage syphilis, which comes with very serious symptoms even 30 years after the initial infection. At that point, the infection can cause paralysis, dementia, blindness, and potentially-fatal damage to your internal organs.Your doctor will first test your blood (or, in some cases, the fluid from a sore) to make sure you actually have syphilis. If you do and you've had the infection for less than a year, you'll get antibiotics and that'll be that. If you've had syphilis for more than a year, you may need more than one dose of antibiotics. Sometimes, treating syphilis in pregnant women can be a challenge because the only recommended treatment for this scenario is penicillin. Women who are allergic to penicillin (the most common drug allergy ) have to go through a desensitization process that allows them to take it. But there aren't any other options, according to the Mayo Clinic . After you've been treated, your doctor will want you to come in for routine blood tests to make sure the antibiotic is working. You'll also have to avoid sexual contact until the blood tests confirm that you're infection-free. And, because many of the symptoms of syphilis can easily go unnoticed, it's extremely important that you tell your sexual partners that you had the infection. (Your local health department has a whole "partner services" section to make that as easy as possible.) From there, it's important to remember that you can get syphilis again — having it once doesn't make you immune. So definitely use safe sex practices to reduce your risk for being infected. That means using a condom (correctly!) every time you have sex, especially if you're not in a monogamous relationship with someone who's tested negative for STIs.