Table of Contents
- The Basics
- Some Sexually Transmitted Infections to Know About
- Protecting Yourself and Others
- The Bottom Line
Sexually transmitted diseases (STDs), also called sexually transmitted infections (STIs), are infections that are passed from person to person through sexual contact. HIV  is an STD. There are more than 25 other sexually transmitted infections that are mainly spread by sexual contact such as vaginal, anal, and oral sex .
Globally, the World Health Organization (WHO) estimates that more than one million people get an STD every day. Most people with sexually transmitted infections do not have any symptoms and are therefore often unaware of their ability to pass the infection on to their sexual partner(s).
If left untreated, sexually transmitted infections can cause serious health problems including cervical cancer , liver disease, pelvic inflammatory disease (PID), infertility, and pregnancy  problems. Having some STIs (such as chancroid, herpes, syphilis, and trichomoniasis) can increase the risk of your getting HIV if you are HIV-negative and get exposed to HIV. People living with HIV (HIV+) may also be at greater risk of getting or passing on other STIs. If and when people living with HIV get STIs, they can experience more serious problems from sexually transmitted infections or have greater difficulty getting rid of sexually transmitted infections.
The US has the highest rate of STIs in the resource-rich world. In the US, about 20 million new infections occur each year. Half of these occur among American young people (15-24 years old), who are more at risk for STDs than older adults. In a report from 2014, the US Centers for Disease Control and Prevention (CDC) reported that for the first time since 2006, the number of people who got chlamydia, gonorrhea, and syphilis (the three nationally reportable STIs) increased. Despite being only a small proportion of sexually active people overall, young people accounted for approximately two-thirds of all new cases of chlamydia and gonorrhea.
There are several reasons why teenage girls and young women are more at risk for sexually transmitted infections. First, the cervix (passage between the vagina and womb) in adolescents and young women is lined with cells that are more likely to become infected with STIs. Second, teenagers and young adults may have problems getting the information and supplies they need to avoid STIs. They may also have trouble getting STI prevention services because they do not know where to find them, do not have transportation to get there, or cannot pay for them. Even if teenagers and young women can get STI prevention services, they may not feel comfortable in places designed for adults. They may also have concerns about confidentiality.
Teenage girls and women of color have some of the highest rates of STIs, especially for chlamydia and gonorrhea. High rates of STIs among women of color are the result of several factors, including higher rates of poverty, less access to health care, and an already high rate of STIs in communities of color. This already high rate of STIs increases the risk of getting an infection each time a woman has sex because she is more likely to have sex with an infected person within her community.
Regardless of race or age, less than half of those who should be tested for sexually transmitted infections receive STI screening. This is especially important for women, since women suffer more frequent and more serious complications from STIs than men.
Many sexually transmitted infections have no symptoms, but can still be passed from person to person. A lot of people who have an STI do not even know it. They may look healthy, and still have an STI. The only way to know for sure is to get tested  - to have regular sexual health screenings by your health care provider. In the US, you can find an STI screening site in your area by looking here .
Fortunately, you can reduce your chances of getting many sexually transmitted infections by practicing safer sex . Most STIs, though not all, can be successfully cured through treatment. For other STIs, there are effective medications that can help you manage your condition.
While many people with sexually transmitted infections show no signs or symptoms of their infection, when there are signs of STIs they are most likely to be in the genital area. The genital area in women includes the vulva (the area around the vagina including the lips), vagina (the opening where menstrual blood comes out), buttocks, urethra (the opening above the vagina where urine comes out) and anus (the opening where a bowel movement comes out). The genital area in men includes the penis, scrotum (“balls”), urethra, and anus.
Some of the most common sexually transmitted infections include those listed below. For pictures of different STIs, please click here  (note: some of these images are graphic).
This sexually transmitted infection is caused by a bacterium. Symptoms may include genital sores, vaginal discharge, a burning feeling when urinating, and swollen lymph nodes in the groin. It can be spread by vaginal or anal sex or skin-to-skin contact with sores. Chancroid can be treated with antibiotics.
This is one of the most common sexually transmitted infections. It is caused by a bacterium that exists in vaginal secretions and semen ("cum"). It can be spread by vaginal, oral, or anal sex without a condom or latex/polyurethane barrier. Pregnant women can pass it on to their babies during delivery. Symptoms may include vaginal discharge and burning during urination, but most women do not have any symptoms. Chlamydia can be successfully treated with antibiotics. If left untreated, it can spread to a woman’s upper, internal reproductive organs (ovaries and fallopian tubes) and cause pelvic inflammatory disease (PID). PID can lead to infertility and make it difficult or impossible to become pregnant .
Yearly chlamydia screening is recommended by the CDC for all sexually-active women under the age of 25, as well as for older women with risk factors such as new or multiple sex partners. Unfortunately, recent reports show that less than half of sexually active women under 26 are screened for chlamydia, in part because of a lack of awareness among health care providers. If you are not offered a chlamydia test, you may want to request one from your health care provider.
Genital warts are caused by viruses. HPV (Human Papillomavirus) is the name of a large group of viruses. Certain types of HPV cause warts on the hands or feet. Other types cause infections in the genital area that can lead to genital warts, cervical cancer , or cancer of the vulva, vagina, anus, and penis. Genital HPV is spread easily through skin-to-skin contact during vaginal, oral, or anal sex. Condoms do not totally prevent transmission. People living with HIV are more likely to be infected with HPV than HIV-negative people. People living with HIV and HPV are also more likely to develop genital warts, as well as cervical or anal cancer.
It is important to find HPV early and get treatment to prevent health problems. Regular cervical screening tests  are a good way to check for HPV. There are also three effective HPV vaccines. Since the introduction of the HPV vaccines several years ago, the number of 14 to 19 year old girls infected with HPV in the US has dropped by more than half. It is important for young people to get vaccinated before they have sex (before they have been exposed to HPV), since people who are already infected with HPV may not be protected by the vaccines. For more information, see our fact sheet on HPV .
Often called “the clap,” this bacterial sexually transmitted infection exists in vaginal secretions and semen. It can be spread through vaginal, anal, or oral sex without a condom or latex/polyurethane barrier. Symptoms may include a yellowish or greenish vaginal discharge and a burning feeling when urinating. Gonorrhea can also affect the anus and the throat. Many women have no symptoms. Gonorrhea can be treated with antibiotics. If left untreated, it can cause PID and infertility. All sexually active women should be screened for gonorrhea.
Hepatitis is an inflammation (irritation) of the liver. Some types of hepatitis are caused by viruses that exist in blood, vaginal secretions, semen, and breast milk. These include hepatitis A  (HAV), hepatitis B  (HBV), and hepatitis C  (HCV), all of which can be sexually transmitted. There is a vaccine to prevent HAV and HBV, but not for HCV. HAV goes away on its own, but HBV and HCV can become chronic (long-term) and very serious. Because HBV and HCV often have no symptoms, most people are not aware that they have the infection. It is important for people living with HIV to be tested for HBV and HCV and treated if necessary. For more information, see our article on Treatment of Hepatitis C in People Living with HIV .
This sexually transmitted infection is caused by a virus that lives in the nerves. There are two common types of herpes. Herpes simplex type 1 (HSV-1) usually causes cold sores around the mouth. Herpes simplex type 2 (HSV-2) usually causes sores in the genital area. However, it is possible to get HSV-2 in the mouth and HSV-1 in the genital area. Symptoms include itchy or painful blisters. The virus is spread through skin-to-skin contact with sores, but it may also spread even before sores can be seen on the infected person. In most people, the sores come and go, but the virus stays in the body for life. Sometimes there are no symptoms because the virus is "hiding" in the nerves. Some women living with HIV never had blisters or sores before they became infected with HIV, and are then surprised when they develop an "outbreak" of sores because their immune systems are weakened by HIV.
Genital HSV-2 infection is more common in women than men. In addition, women living with HIV may have more frequent or difficult to treat herpes outbreaks. There is no cure for herpes, but the antiviral drugs Zovirax (acyclovir), Valtrex (valacyclovir), and Famvir (famciclovir) can reduce the number of outbreaks if taken daily and can shorten outbreaks and make them less severe if taken as soon as symptoms begin. Valtrex has also been shown to lower your risk of passing the infection to someone else. Pregnant women can pass herpes to their babies, so it is important to let your health care provider know if you have genital herpes and you are pregnant  or planning to become pregnant .
HIV stands for Human Immunodeficiency Virus. HIV is the virus that causes AIDS. It is present in blood, vaginal secretions, semen, and breast milk. HIV can be spread through vaginal, oral, or anal sex without a condom or latex/polyurethane barrier. As many as one in five people living in the US do not know they are infected. Many people living with HIV look and feel healthy and do not think they are at risk for becoming sick or passing HIV to others.
Getting tested  for HIV is part of routine, regular health care in many countries. The Public Health Agency of Canada, for example, recommends that HIV testing be discussed as part of routine medical care. The CDC now recommends testing all people ages 13 to 64, unless they have already been tested. It is also recommended that you get tested for HIV before beginning a new sexual relationship, regardless of your age.
The World Health Organization (WHO) makes different suggestions based on where you live. Where HIV is widespread, it recommends that HIV testing be offered to anyone who goes to a healthcare facility. Where HIV is less common, it suggests that HIV tests be offered to people who may be at higher risk of having been exposed to HIV.
It is important that you also get tested if:
- You have ever had vaginal, anal, or oral sex without a condom
- You have ever shared needles or syringes to inject drugs or other substances
- You are uncertain of your partner’s status or your partner is living with HIV
- You are pregnant  or are considering becoming pregnant 
- You have ever been diagnosed with a sexually transmitted infection or disease
- You have hepatitis C 
- You begin treatment for tuberculosis (TB) 
If left untreated, HIV can cause serious illness and death. If you test HIV+ there are effective medications to help you stay well. But you cannot get the health care and treatment you need if you do not know your HIV status. For more information on HIV, go to the section on The Well Project website called HIV: The Basics .
Pubic Lice (“Crabs”)
Pubic lice live in the pubic hair and can be transmitted by skin-to-skin contact. They can also be spread through infected clothes and bedding. Symptoms may include intense itching and seeing lice or eggs in the hair. Pubic lice can be treated with over-the-counter medications. However, pregnant women must use products specially designed for them. Contaminated clothes, sheets, pillowcases, blankets, and towels should be washed in hot water and laundry soap to kill lice and eggs and to prevent being infected again.
This sexually transmitted infection is caused by a bacterium. It can be spread by vaginal, anal, or oral sex without a condom or latex/polyurethane barrier. The disease has several phases. People with primary syphilis (early disease) may have pain-free open sores, called chancres, in the genital or anal area or around the mouth. The sores usually heal on their own in three to six weeks. People with secondary syphilis (a later stage of the disease) often have a rash and/or hair loss. If left untreated, syphilis can proceed to the latent stage during which it may have no visible symptoms but can cause damage to the heart, brain, and other organs. Syphilis can be successfully treated with antibiotics. Without treatment, it can hurt your body’s organs, leading to severe illness and even death. Pregnant women can pass syphilis to their babies during pregnancy and childbirth, so it is important that pregnant women get tested for syphilis.
This sexually transmitted infection is caused by a single-celled germ called a protozoa. It can be spread during vaginal, oral, or anal sex without a condom or latex/polyurethane barrier. Trichomoniasis is a common cause of vaginal infections. Symptoms may include a foamy, foul-smelling vaginal discharge and itching. Sometimes there are no symptoms at all. Trichomoniasis can be successfully treated with antibiotics. When a woman is infected with trichomoniasis, she and her sexual partner must both be treated, or the untreated partner can re-infect her.
You can greatly reduce your risk of getting many sexually transmitted infections by practicing safer sex . Some STIs like genital warts, herpes, and syphilis can be spread through contact with infected skin. Here are some tips for protecting yourself:
- Use a latex condom for vaginal and anal sex or a plastic condom if you are sensitive to latex
- The female condom can also prevent many sexually transmitted infections
- Use condoms without lubricant for oral sex on a man
- Use latex or plastic barriers, such as a dental dams or plastic wrap, for oral sex on a woman or for oral-anal sex; use latex or plastic gloves if you have cuts or sores on your hands
- Use water-based lubricants (KY, Astroglide) with latex condoms or barriers
- DO NOT use oil-based products (Vaseline, body lotions) because they destroy latex
- Do not use lubricants or condoms that contain nonoxynol-9 (N-9), which can damage the lining of the vagina or anus and increase the chances of infection with HIV
- Wash shared sex toys (dildos, vibrators) or put on a fresh condom between users
- Know that some methods of birth control , like birth control pills, shots, implants, or diaphragms, will not protect you from sexually transmitted infections. If you use one of these methods also use a latex condom.
- Talk with your sex partner(s) about sexually transmitted infections and using condoms 
- Talk honestly with your health care provider and your sex partner(s) about any sexually transmitted infections you or your partner has or has had
- Have regular pelvic exams and cervical cancer screening, but remember that cervical cancer screening tests do not screen for sexually transmitted infections other than HPV
- Talk to your health care provider about having routine sexually transmitted infection screening as part of your annual physical or gynecological exam 
- Do not share needles or syringes for injecting drugs or other substances; if you do share drug equipment, be sure to clean your works 
There are many sexually transmitted infections including HIV. Some can be cured with treatment. Some, like HIV and herpes, cannot be cured, but can be managed. Many can cause serious health and fertility problems or even death if left untreated. Practicing safer sex  can protect you from many, but not all, sexually transmitted infections.
See your health care provider right away about sexually transmitted infections if:
- You have had sexual contact with someone who may have a sexually transmitted infection
- You have symptoms like genital sores, discharge, or burning when you urinate
- You are pregnant
It is important for you to get tested regularly for sexually transmitted infections if you (1) are sexually active, (2) have sex with more than one partner or (3) your partner has sex with people other than you. Many STIs do not have symptoms. If needed, get the treatment your health care provider recommends. Even if the symptoms go away, you still need to finish treatment. If symptoms continue after treatment, see your health care provider. Also make sure your partner(s) gets treated, so that you do not pass an infection back and forth.