How common are sexually transmitted infections (STIs) in the United States (all STDs are STIs)?
The United States has an epidemic of sexually transmitted infections (STIs). Over 70 million Americans currently have an STI. Twenty million new cases occur each year. Half of these are in people under 25. Three STIs (human papillomavirus, trichomoniasis and chlamydia) accounted for 88% of all new cases of STI among 15- to 24-year-olds.