 We explain sexually transmitted infections, known as STIs or STDs. STIs are infections that are spread by sex. Unfortunately, most STIs initially do not cause symptoms, which increases the risk of passing the disease onto others. Signs of disease may include vaginal and penile discharge, ulcers on or around the genitals, and pelvic pain. Diagnostic tests are easily available, and for doctors STIs are not unusual, so there is no reason to be ashamed or afraid of addressing the topic. Tests include blood, urine, vaginal swabs in women or urethral swabs in men. There are more than 30 different bacteria, viruses, and parasites that can cause STIs. Usually spread by sex, some STIs can also be caught by non-sexual contact with contaminated blood and tissues, breastfeeding, or even during child's birth. Tests of these infections are treatable or curable. Some of the most common infections, like syphilis and chlamydia, are curable, while HIV is treatable but not curable. Nevertheless, resistance to certain antibiotics is developing, which makes gonorrhea more and more difficult to cure. Mostly, STIs are treated with antibiotics or antiviral drugs. When receiving treatment, remember that recent sexual partners should be treated as well. If you are diagnosed with an STI, you should always inform your partner so they can receive treatment too. The most effective way to prevent STIs is to just not have sex. As not everyone lives as a celibate, safer sex practices should be applied. The use of condoms, having a small number of sexual partners, and being in a monogamous relationship decreases the risk of becoming infected.