Sexually transmitted infections, sometimes abbreviated as STIs or STDs, are common infections that spread from one person to another during sex. They're so common that most sexually active people will get at least one in their lifetime. Often there are no symptoms, but if left untreated, STIs can cause serious health issues, and in some cases, death.
Not all STIs are transmitted the same way. Some STIs, like gonorrhea and chlamydia, are transmitted by bodily fluids. Other STIs, like syphilis or herpes, are passed by skin-to-skin contact.
The good news is that all STIs, including HIV, are treatable, and many are curable.
Learn more facts about STIs, HIV, and viral hepatitis:
Chlamydia is one of the most common STIs with an estimated 1.7 million new cases a year in the U.S. Many people who have chlamydia do not know it. Often there are no symptoms. If left untreated, chlamydia can cause infertility and pain in both women and men. Once diagnosed, it is easily cured with antibiotics. For more information, see the CDC's chlamydia fact sheet.
Gonorrhea is common, especially among teens and people in their 20s. Sometimes called "the clap" or "the drip," gonorrhea may not show symptoms. Left untreated, it can cause infertility and pain in both women and men. Once diagnosed, it is easily cured with antibiotics. For more information, see the CDC's gonorrhea fact sheet.
Viral hepatitis is a serious but preventable condition that affects the liver. The three most common types of viral hepatitis are A, B, and C, and each can be transmitted from person to person in different ways. There are many ways a person can reduce the likelihood of acquiring viral hepatitis: Get vaccinated for hepatitis A and hepatitis B. Practice safer sex. Practice safer drug use. Practice good personal hygiene, such as thorough handwashing. Hepatitis A and B are preventable, and hepatitis C is curable. For more information, see the CDC's viral hepatitis fact sheets.
Herpes is an STI that can cause sores on the genitals and/or mouth. An estimated one in six people in the U.S. has genital herpes, and there is no cure. Still, prescription medication can ease symptoms and lower the chances of passing the virus to others. Herpes can be painful but usually does not lead to serious health problems. For more information, see the CDC's herpes fact sheet.
HPV is the most common STI with an estimated 14 million new cases in the U.S. each year. There are more than 150 different types of HPV, and while some forms of HPV cause genital warts, many do not show any symptoms. Some forms can be severe and lead to cancer. The HPV vaccine protects against specific types of HPV associated with genital warts and cervical cancer. For more information, see the CDC's HPV fact sheet.
Trichomoniasis, sometimes called "trich" for short, often does not show any symptoms. An estimated 3.7 million people are living with trich in the U.S. Trich is usually not serious and can be cured in most cases. Once diagnosed, it is easily cured with antibiotics. For more information, see the CDC's trichomoniasis fact sheet.