As many as one in ten Americans have HPV, and some studies show that at least one-third of all sexually active young adults have genital HPV infections. It is often stated that more than half of all college-age women wil become infected with HPV during their college career.
About one in five people in the United States over age 12 -- approximately 45 million individuals -- are infected with HSV-II, the virus that causes genital herpes. Around 50 - 80% of the adult population has oral herpes, which most people contract through nonsexual contact in childhood.
Chlamydia is the most common bacterial infection (STI) in the United States, with about 3 million new cases reported annually. Chlamydia ("cla-mid-ee-ah") is so common in young women that, by age 30, 50% of sexually active women have evidence that they have had chlamydia at some time during their lives.