Aside from colds and the flu, sexually transmitted diseases (STDs) are some of the most widespread diseases both in the United States and the world. STDs affect both men and women, and two-thirds of all STDs occur in people younger than 25 years old. Exposure to an STD can occur any time you have sexual contact with anyone that involves the genitals, the mouth (oral), or the rectum (anal). Exposure is more likely if you have more than one sex partner or do not use condoms. Some STDs can be passed by nonsexual contact, such as by sharing needles or during the delivery of a baby or during breast-feeding. Sexually transmitted diseases (STDs) are also called sexually transmitted infections (STIs).

STDs are a worldwide public health concern because there is more opportunity for STDs to be spread as more people travel and engage in sexual activities. Some STDs have been linked to an increased risk of certain cancers and infection with human immunodeficiency virus (HIV). Pregnant women can spread STDs to their babies. Many people may not have symptoms of an STD but are still able to spread an infection. STD testing can help find problems early on so that treatment can begin if needed. It is important to practice safe sex with all partners, especially if you or they have high-risk sexual behaviors. See the Prevention section of this topic.

Common sexually transmitted diseases

There are at least 20 different STDs. They can be caused by viruses, bacteria and protozoa. Some of the most common STDs in the U.S. are:

• Chlamydia.
• Genital herpes.
• Genital warts or human papillomavirus (HPV). Certain high-risk types of HPV can cause cervical cancer in women.
• Gonorrhea.
• Hepatitis B.
• Syphilis.
• Trichomoniasis.
• Human immunodeficiency virus (HIV), which causes AIDS. Having other STDs, such as genital herpes, can increase your risk of HIV.
• Other infections that may be sexually transmitted. These include hepatitis A, cytomegalovirus, molluscum contagiosum, bacterial vaginosis, Mycoplasma genitalium, and possibly hepatitis C.
• Scabies and pubic lice, which can be spread by sexual contact.

Bacterial STDs can be treated and cured, but STDs caused by viruses usually cannot be cured. You can get a bacterial STD over and over again, even if it is one that you were treated for and cured of in the past.

For more information on the symptoms, treatment, and possible complications of specific STDs, see the specific topic in Related Information.

Sexually active teens and young adults

Sexually active teenagers and young adults are at high risk for STDs because they have biological changes during the teen years that increase their risk for getting an STD and they may be more likely to:

• Have unprotected sex.
• Have multiple partners.
• Engage in high-risk sexual behaviors.