1. STDS/STIS Sexually Transmitted Disease Sexually Transmitted Infection:
Medically, infections are only called diseases when they cause symptoms. That is why STDs are also called "sexually transmitted infections.”

2. STDs/STIs
Sexually transmitted diseases (STDs) are caused by infections that are passed from one person to another during sexual contact. You can get a sexually transmitted disease from sexual activity that involves the mouth, anus, vagina, or penis.
These infections often do not cause any symptoms.
STDs can affect guys and girls of all ages and backgrounds who are having sex — it doesn't matter if they're rich or poor.

3. How are STDs/STIs Transmitted
You can get a sexually transmitted disease from:
Sexual activity that involves the mouth, anus, vagina, or penis
Through body fluids, mucous membranes, or broken skin, blood or muscle transfusion
Sharing needles, syringes, or other injection equipment
Having contact with infected objects, clothing, and/or bed linen