Sexually transmitted infections (STIs) are also known as sexually transmitted diseases (STDs). It’s useful to be familiar with both terms, as some health care providers may still use both, but the sexual health community has shifted mostly to the use of the term STI to emphasize that one may be infected with an STI without showing symptoms of a disease.
STI symptoms vary by infection. Changes in odor, color, and texture of penile or vaginal discharge, as well as visible lesions, bumps, redness, itching and tenderness are common symptoms of some STIs. However, the most common symptom of an STI is to have no symptoms at all.
STIs are generally discussed in one of three categories: viral, bacterial, and other. The main difference between these categories is what causes them and how they are subsequently treated. STIs can be spread by the exchange of bodily fluids and skin-to-skin contact. Semen, blood (including menstrual blood), and vaginal secretions are the most likely to transmit STIs; fluids such as saliva, sweat, and urine are unlikely to transmit STIs, though they can still transmit some bacteria and viruses.