Series

The STI Files

Clear and in-depth information about all known and current infections or other kinds of illness that can be transmitted through consensual sex⁠ , sexual⁠ violence or other kinds of intimate contact.

Articles in this series

Bacterial vaginosis (BV) is the most common cause of vaginitis symptoms among people with vaginas of childbearing age (15-45). However, half the people who meet clinical criteria for BV have no symptoms.

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.

One member of a group of herpes-type viruses, CMV is transmitted through body fluids, sexually and nonsexually, and from mother to infant during birth. CMV is also incredibly dangerous for people who are immunocompromised or people with HIV.

In the United States, approximately 75% of all reported gonorrhea is found in people age 15 to 29.

Hepatitis is is an inflammation of the liver almost always caused by different hepatitis viruses. Learn about prevention and treatment for hepatitis A, B, C, and beyond.

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 percent of the adult population has oral herpes, which most people contract through nonsexual contact in childhood.

HIV is a virus that destroys the immune system and thus weakens the body's ability to fight disease and infection, even common infections like flus and colds. HIV usually progresses to AIDS. This makes HIV the most dangerous sexually transmitted infection today. It is the fifth leading cause of death for the young under 40 in the United States. At this time, no one has been cured of HIV or AIDS.

As many as one in four Americans have HPV.

Molluscum contagiosum -- a bumpy skin infection -- isn't technically an STI, but can be transmitted through sexual contact. The CDC states that molluscum cases in the United States have been on the rise since 1996.

Mycoplasma genitalium (sometimes called Mgen) is a bacterial infection spread through sexual contact. Although it's pretty common now, it isn't diagnosed and treated as often as it should be.

"Pelvic inflammatory disease" is shorthand for any serious bacterial infection of the reproductive organs that are housed in the pelvis: the uterus, uterine lining, fallopian tubes, and/or ovaries. These infections usually start in the vagina and, when left untreated, can progressively infect other reproductive organs. 20% of PID cases are found in teens, who often are afraid or unable to get reproductive health care. PID can result in permanent infertility and chronic pain.

Pubic lice is also called "crabs." It's caused by very tiny insects that live in pubic hair and feed on human blood. Pubic lice are often spread through sexual contact, though genital contact or sexual intercourse is not necessary for transmission. I

This disease has bothered humans for thousands of years, but it seems to come and go in unexplainable cycles. Scabies used to be very rare in America, but now it is coming back again.

Syphilis has been called "the great imitator" because many of its signs look like other diseases. It is also difficult to know if someone has syphilis because a person might not have any symptoms at all.

Trichomoniasis is one of the most common sexually transmitted diseases, mainly affecting 16-to-35-year old females.

While most cases of Zika virus are acquired via mosquito bites, this emerging virus can be transmitted sexually, and the CDC reports that the numbers of such cases are growing in subtropical regions of the Americas.