Sexual activity includes vaginal, anal, and oral sex. Most STD germs need to live in warm, moist areas. That's why they infect the mouth, rectum and sex organs of both males and females. The STDs of HIV and Hepatitis B are also spread by contact with infected blood. STD's are dangerous because they place a person at risk for infertility, cancer, or an incurrable illness like Herpes, AIDS, or Hepatitis.
Many people have no symptoms.
If you have any of these symptoms, stop having sex. Go to the doctor to get checked and treated. Don't have sex until your treatment is complete. You can protect yourself. Abstinence, which is no sexual contact, is your best defense.