By the end of this lesson, participants will be able to:

1. Explain how easily a sexually transmitted infection (STI) can spread with unprotected intercourse.

2. Describe how common STIs are in the United States and explain the differences between bacterial STIs and viral

3. Assess their own behavior for risk of sexually transmitted infections.


One of the greatest deterrents to the practice of safer sex is the mindset “it can’t happen to me.” Yet statistics show that, in the United States, there are 19 million new cases of sexually transmitted infections each year and that young people aged 15-24 account for almost half of those new cases.[1] This lesson dramatizes the rapid geometric progression possible in the spread of a sexually transmitted infection and encourages participants to think about the reasons why many people do not protect themselves. It uses incidence and prevalence charts to demonstrate the large number of people who are infectious and emphasizes the importance of honest assessment of one’s own risk.

Note: There is an alternate version for teaching this lesson that is included after the handouts.

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