How common are STIs?
The United States has an epidemic of sexually transmitted infections (STIs). Over 70 million Americans currently have an STI. 19 million new cases occur each year. Half of these are in people under 25. What causes STIs? STIs can be caused by bacteria (eg, chlamydia, gonorrhea, syphilis), viruses (eg, HIV/AIDS, hepatitis, herpes, HPV), or parasites (trichomoniasis). Chlamydia is the most common bacterial STI. Human papillomavirus (HPV) infection is the most common viral STI. How do you get them? You get STIs during sexual activity. This includes vaginal sex, oral sex and anal sex. A few—HPV and herpes—can even be spread by contact with infected skin. Others, such as HIV and hepatitis, can be spread through needle-sharing. You can get STIs from someone who has no symptoms. What are the symptoms? Many people with STIs have no symptoms. Even without symptoms, they can still pass on the infection. Some STIs cause symptoms such as an abnormal discharge from the penis or vagina, burning sensa
