STD (Sexually transmitted diseases) or STI (sexually transmitted infections) are generally received by sexual contacts. Bacteria, viruses or parasites that cause sexually transmitted diseases may transfer from person to person through blood, semen, saliva, vaginal fluids, and other fluids from human body.
These infections can be also transmitted without sexual intercourse, such as from mothers to toddlers during pregnancy or delivery of baby, or through blood transfusions or shared needles. STDs don’t always cause symptoms. It’s even possible to obtain STD from people who look perfectly healthy and may not even know if they have an infection.