American Sexual
Health Association

STIs A to Z

Sexually transmitted infections, or STIs—also called sexually transmitted diseases, or STDs—affect people of all ages, backgrounds, and from all walks of life. In the U.S. alone there are about 20 million new cases each year, about half of which are in young people ages 15-24 years.

Getting the facts about STIs and sexual health is increasingly important. We invite you to explore our website and learn more about specific STIs, tips for making sex safer, and ways to talk with healthcare providers and partners.

Learn More About STIs

WATCH: An Overview of Common STIs, STI Testing, and Treatment

Experts Chase Cannon and Stacey Griner provide a comprehensive overview of STIs today and what everyone should know about STIs and testing.


While you’ll see both terms used, there has been a shift in recent years to STI. Why? The concept of “disease,” as in STD, suggests a clear medical problem, usually some obvious signs or symptoms. But many common STDs have no signs or symptoms in most of the people who have them. Or they have mild signs and symptoms that can be easily overlooked. So the sexually transmitted virus or bacteria can be described as creating “infection,” which may or may not result in “disease.” This is true of chlamydia, gonorrhea, herpes, and human papillomavirus (HPV), to name a few.

But there is not consensus in the medical and public health community, as H. Hunter Handsfield, MD, Professor Emeritus at Washington University Center for AIDS and STD notes in his essay for the journal Sexually Transmitted Diseases. While making arguments for both terms, Handsfield suggests, “Those who prefer either term should use it freely, with neither defensiveness nor pride in either one.” Read his thoughts here..

Or is it time for a new term? Medical linguist Janet Byron Anderson, PhD, argues that we do and proposes “sexually transmissible infectious disease (STID).” You can read her take here.