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STDs Today

With nearly 20 million new sexually transmitted disease (STD) infections occurring each year, half of them among young people ages 15 to 24 (1), prevention of STDs is more important than ever. STDs affect men and women of all backgrounds and economic levels, and add an estimated $16 billion to the nation's healthcare costs each year (1).

Despite the fact that STDs are extremely widespread, most people in the United States remain unaware of the risk and consequences of all but the most prominent STD—HIV, the virus that causes AIDS. NPIN provides the latest information on the current state of STD infection in the United States, who is at risk, and what is being done about it. The links below will help you get started.

Who is Infected
What Are Some Health Risks of STD Infection?
What is Being Done?
Common STDs
         Acquired Immune Deficiency Syndrome (AIDS)
         Bacterial Vaginosis
         Genital Herpes/HSV
         Genital HPV Infection
         Viral Hepatitis
         Other STDs

Who is Infected?

In the United States alone, an estimated 19 million new STD infections occur each year (1). This table shows the incidence and prevalence of some of the most common STDs from the years that data was last available.

STD Incidence *
* Estimated number of annual new cases
Chlamydia 1,422,976 (1)
Gonorrhea 334,826 (1)
Syphilis (primary and secondary) 15,667 (1)
Hepatitis B (HBV) 18,800 (2)
Hepatitis C (HCV) 16,500 (2)
Human Papillomavirus (HPV) 14 million (3)

Variations in risk

STDs affect men and women of all backgrounds and economic levels. However, there are clear disparities.

  • Trend data available for the first time show that men who have sex with men (MSM) now account for three quarters (75 percent) of all primary and secondary syphilis cases (1).

  • The numbers and rates of reported chlamydia and gonorrhea cases are highest in Americans between the ages of 15 and 24 (1).

  • Women and infants bear significant long-term consequences of STDs. In addition to biological and social factors such as poverty and access to quality STD services, a woman’s inability to negotiate safer sexual practices, such as condom use, can significantly affect her sexual health and subsequently the health of her unborn baby (4).

  • Surveillance data show higher rates of reported STDs among some racial or ethnic minority groups when compared with rates among whites. Race and ethnicity in the United States are population characteristics that correlate with other fundamental determinants of health status (4).

For more information on at-risk populations, visit the Communities at Risk section of this Web site.

What Are Some Health Risks of STD Infection?

STDs can result in irreparable lifetime damage for infants infected by their mothers during gestation or birth, including blindness, bone deformities, mental retardation, and death.

If left untreated in women, STDs can lead to pelvic inflammatory disease (PID), infertility, potentially fatal ectopic pregnancies, and cancer of the reproductive tract. In men, untreated STDs can lead to sterility, cancers of the penis and anus, and swollen or tender testicles, among other complications.

What Is Being Done?

Prevention—both biomedical and behavioral—is the best hope for reducing or eliminating STDs.

As the lead agency for STD prevention in the United States, CDC is tasked with providing national leadership through research, policy development, and support of effective services to prevent STDs (including HIV infection) and their complications, such as enhanced HIV transmission, infertility, adverse outcomes of pregnancy, and reproductive tract cancer. The Division of STD Prevention, part of CDC's National Center for HIV, Viral Hepatitis, STD, and TB Prevention, coordinates CDC's STD prevention efforts through national leadership on policy development, research, and support of effective prevention services. Visit NPIN’s Prevention Today page to learn more about CDC’s prevention strategy, and check out our Education and Outreach section for more information on STD prevention programs that work.


Common STDs

Many people are aware of the most prominent STD—HIV. However, many other STDs affect millions of men and women each year. Did you know:

  • Many STDs initially cause no symptoms, especially in women?
  • When symptoms develop, they may be confused with those of other diseases that are not transmitted through sexual contact?
  • STDs can still be transmitted from person to person even if they do not show symptoms?
  • Health problems caused by STDs tend to be more severe for women than for men?

Below are descriptions of several of the most common STDs, including information about incidence, symptoms (if any), and treatment.

    Acquired Immune Deficiency Syndrome (AIDS)

    Acquired Immune Deficiency Syndrome (AIDS) Acquired immune deficiency syndrome (AIDS) was first reported in the United States in 1981. AIDS is caused by the human immunodeficiency virus (HIV), a virus that destroys the body's ability to fight off infection.

    People who have AIDS are very susceptible to many life-threatening diseases, called opportunistic infections, and to certain forms of cancer. Transmission of the virus primarily occurs during unprotected sexual activity and by sharing needles used to inject intravenous drugs.

    Learn more about AIDS and HIV. En Español.

    Bacterial Vaginosis

    Bacterial vaginosis (BV) is a condition in women where the normal balance of bacteria in the vagina is disrupted and replaced by an overgrowth of certain harmful bacteria. It is the most common vaginal infection in women of childbearing age. Most women report no signs or symptoms of infection, but symptoms sometimes include vaginal discharge, odor, pain, itching, or burning.

    Any woman can get BV. However, some activities or behaviors can upset the normal balance of bacteria in the vagina and put women at increased risk, including having a new sex partner or multiple sex partners and douching. In most cases, BV causes no complications, but there are some serious risks from BV including:

    • Increased susceptibility to HIV infection and other STDs.
    • Increased chances that an HIV-infected woman can pass HIV to her sex partner.
    • Increase chances of developing an infection following surgical procedures such as a hysterectomy or an abortion.
    • Increased risk for some complications of pregnancy, such as preterm delivery or low birth weight.

    Although BV will sometimes clear up without treatment, all women with symptoms of BV should be treated to avoid complications. Male partners generally do not need to be treated. However, BV may spread between female sex partners. BV is treatable with antibiotics prescribed by a health care provider.

    Learn more about BV.


    ChancroidChancroid ("SHAN-kroid") is a bacterial infection caused by Haemophilus ducreyi, which is spread by sexual contact and results in genital ulcers. The disease is found primarily in developing and Third World countries.

    The infection begins with the appearance of painful open sores on the genitals, sometimes accompanied by swollen, tender lymph nodes in the groin. These symptoms occur within a week after exposure. Symptoms in women are often less noticeable and may be limited to painful urination or defecation, painful intercourse, rectal bleeding, or vaginal discharge. Chancroid lesions may be difficult to distinguish from ulcers caused by genital herpes or syphilis. A physician must therefore diagnose the infection by excluding other diseases with similar symptoms. Chancroid is one of the genital ulcer diseases that may be associated with an increased risk of transmission of the human immunodeficiency virus (HIV), the cause of AIDS.

    People with chancroid can be treated effectively with one of several antibiotics.

    Learn more about chancroid infection. En Español.


    ChlamydiaChlamydial ("kla-MID-ee-uhl") infection is a common STD caused by the bacterium Chlamydia trachomatis. Chlamydia is the most frequently reported bacterial STD in the United States.

    Chlamydia can be transmitted during vaginal, oral, or anal sexual contact with an infected partner. A pregnant woman may pass the infection to her newborn during delivery, with subsequent neonatal eye infection or pneumonia. Irreversible damage, including infertility, can occur “silently” before a woman ever recognizes a problem. Because symptoms of chlamydia are usually mild or absent, it can progress and damage a woman's reproductive organs and cause serious complications. Chlamydia also can cause discharge from the penis of an infected man, but complications among men are rare.

    Pelvic inflammatory disease (PID), a serious complication of chlamydial infection, has emerged as a major cause of infertility among women of childbearing age. PID can cause infertility or damage the fallopian tubes enough to increase the future risk of ectopic pregnancy and infertility. Ectopic pregnancy is a life-threatening condition in which a fertilized egg grows outside the uterus, usually in a fallopian tube which can rupture.

    Chlamydia can be easily treated and cured with antibiotics.

    Learn more about Chlamydia. En Español.

    Genital Herpes/HSV

    Genital Herpes/HSV Genital herpes is a contagious viral infection caused by the herpes simplex virus (HSV). There are two types of HSV: herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). Both can cause genital herpes, although most genital herpes is caused by HSV-2.

    Most individuals have no or only minimal signs or symptoms from HSV-1 or HSV-2 infection. HSV-1 most commonly causes sores on the lips (known as fever blisters or cold sores), but it can cause genital infections through oral-genital or genital-genital contact. HSV-2 symptoms typically appear as one or more blisters on or around the genitals or rectum. Occasionally, sores also appear on other parts of the body where broken skin has come into contact with HSV. The virus remains in certain nerve cells of the body for life, causing periodic symptoms in some people.

    HSV-1 and HSV-2 can be found in and released from the sores that the viruses cause, but they also are released between outbreaks from skin that does not appear to have a sore. Generally, a person can only get HSV-2 infection during sexual contact with someone who has a genital HSV-2 infection. Transmission can occur from an infected partner who does not have a visible sore and may not know that he or she is infected.

    There is no treatment that can cure herpes, but antiviral medications can shorten and prevent outbreaks during the period of time the person takes the medication.

    Learn more about genital herpes. En Español.

    Genital HPV Infection

    Genital HPV InfectionHuman papillomavirus (HPV) is the most common STD. There are more than 40 HPV types that can infect the genital areas of males and females. These HPV types can also infect the mouth and throat.

    Low-risk types of HPV cause genital warts, the most recognizable sign of genital HPV infection. Other high-risk types of HPV cause cervical cancer and other genital cancers.

    Most people with HPV do not develop symptoms or health problems. In most cases, HPV goes away on its own and does not cause any health problems.

    HPV is passed on through genital contact, most often during vaginal and anal sex. HPV may also be passed on during oral sex and genital-to-genital contact. HPV can be passed on between straight and same-sex partners—even when the infected partner has no signs or symptoms.

    Vaccines can protect males and females against some of the most common types of HPV. These vaccines are given in three shots. It is important to get all three doses to get the best protection. The vaccines are most effective when given before a person's first sexual contact, when he or she could be exposed to HPV.

    Learn more about human papillomavirus. En Español.


    Gonorrhea Gonorrhea ("gone-or-REE-uh") is caused by Neisseria gonorrhoeae, a bacterium that can grow and multiply easily in the warm, moist areas of the reproductive tract. . Gonorrhea can be transmitted during vaginal, oral, or anal sexual contact with an infected partner.

    Symptoms of infection include a discharge from the vagina or penis and painful or difficult urination. The most frequent and serious complications occur in women and, as with chlamydial infection, these complications include  pelvic inflammatory disease (PID), ectopic pregnancy, and infertility.

    Gonorrhea can grow in the cervix (opening to the womb), uterus (womb), and fallopian tubes (egg canals) in women and in the urethra (urine canal) in women and men. The bacterium can also grow in the mouth, throat, eyes, and anus. It can be life-threatening if it spreads to the blood or joints. In addition, people with gonorrhea can more easily contract HIV, the virus that causes AIDS. HIV-infected people with gonorrhea are more likely to transmit HIV to someone else.

    Several antibiotics can successfully cure gonorrhea in adolescents and adults. However, antibiotic-resistant strains of gonorrhea are increasing in many areas of the world, and successful treatment of gonorrhea is becoming more difficult. New antibiotics or combinations of drugs must be used to treat these resistant strains.

    Learn more about gonorrhea. En Español.


    Syphilis Syphilis ("SIF-i-lis") is caused by the bacterium Treponema pallidum. The incidence of syphilis has increased and decreased dramatically in recent years.

    Syphilis is passed from person to person through direct contact with syphilis sores. The first symptoms of syphilis infection may go undetected because they are very mild and disappear spontaneously. The initial symptom is a chancre (genital sore); it is usually a painless open sore that most often appears on the penis or around or in the vagina. It can also occur near the mouth, anus, or on the hands. Transmission of the organism occurs during vaginal, anal, or oral sex. Pregnant women with the disease can pass it to the babies they are carrying.

    If untreated, syphilis may go on to more advanced stages, including a transient rash, and eventually can cause serious involvement of the brain, nerves, eyes, heart, blood vessels, liver, bones, and joints. The full course of the disease can take years.

    Chancres caused by syphilis make it easier to transmit and acquire HIV infection sexually.

    Penicillin remains the most effective drug to treat people with syphilis. For people who are allergic to penicillin, other antibiotics are available to treat syphilis.

    Learn more about syphilis. En Español.


    Trichomoniasis (“trick-oh-moe-NYE-uh-sis”) is caused by the single-celled protozoan parasite, Trichomonas vaginalis. It is the most common curable STD in young, sexually active women, and it affects men as well although symptoms are most common in women.

    The vagina is the usualsite of infection in women, and the urethra (urine canal) is the usual site of infection in men. The parasite is sexually transmitted through penis-to-vagina intercourse or vulva-to-vulva (the genital area outside the vagina) contact with an infected partner. Women can acquire the disease from infected men or women, but men usually contract it only from infected women.

    Most men with trichomoniasis do not have signs or symptoms; however, some men may temporarily have an irritation inside the penis, mild discharge, or slight burning after urination or ejaculation. Some women have signs or symptoms of infection that include a frothy, yellow-green vaginal discharge with a strong odor. The infection also may cause discomfort during intercourse and urination, as well as irritation and itching of the female genital area.

    Trichomoniasis can usually be cured with prescription drugs, either metronidazole or tinidazole, given by mouth in a single dose.

    Learn more about trichomoniasis. En Español.

    Viral Hepatitis

    Hepatitis A is a contagious liver disease caused by the hepatitis A virus (HAV). Infection with hepatitis A can result in a mild illness lasting a few weeks to a severe illness lasting several months. HAV infection is primarily transmitted by ingestion of fecal matter, even in tiny amounts, from close person-to-person contact with an infected person, sexual contact with an infected person, ingestion of the virus from contaminated food, drink, or objects. Hepatitis A vaccination is the most effective measure to prevent HAV infection and is recommended for men who have sex with other men, those who use recreational drugs (whether injected or not), and international travelers. All children are now vaccinated for HAV infection at age one.

    Hepatitis B Hepatitis B s a contagious liver disease caused by hepatitis B virus (HBV). HBV infection can result in a short term illness or it can result in a chronic or lifelong infection. Chronic infection can lead to cirrhosis (scarring) of the liver, liver cancer, liver failure, and death. HBV is transmitted through percutaneous (puncture through the skin) or mucosal contact with infectious blood or body fluids. Most newly infected people get hepatitis B through sexual contact or sharing injection drug equipment. Hepatitis B vaccination is the most effective measure to prevent HBV infection and is recommended for adults at risk for HBV infection, as well as all infants.

    Hepatitis C is a contagious liver disease caused by the hepatitis C virus (HCV) that sometimes results in a short term illness, but most often becomes a chronic or lifelong infection that can lead to cirrhosis (scarring) of the liver, liver failure, liver cancer, and death. Liver damage often occurs silently. In the United States, an estimated 3.2 million persons are chronically infected with hepatitis C, most of whom do not know they are infected since they have no symptoms. HCV is spread by contact with the blood of an infected person, primarily through sharing injection drug equipment or receiving blood transfusion prior to widespread screening in 1992. Having a sexually transmitted disease or HIV appears to increase a person’s risk for hepatitis C. There also appears to be an increased risk of hepatitis C transmission among gay men who are HIV-positive. There is no vaccine for hepatitis C. If a person thinks they might have been exposed to hepatitis C, they should talk to a doctor about getting tested.

    Learn more about viral hepatitis.

    Other STDs

    Other diseases that may be sexually transmitted include scabies, pubic “crab” lice, and Pelvic Inflammatory Disease (PID).

1 CDC. Reported STDs in the United States, 2012 National Data for Chlamydia, Gonorrhea, and Syphillis, Atlanta: U.S. Department of Health and Human Services; 2014. [cited 2014 24 March]. Available from: (PDF).
2 CDC. Disease Burden from Viral Hepatitis A, B, and C in the United States. Atlanta: U.S. Department of Health and Human Services; 2012. [cited 2014 March 26]. Available from:
3 CDC. Genital HPV Infection. Atlanta: U.S. Department of Health and Human Services; 2013. [cited 2014 March 26]. Available from:
4 CDC. 2012 Sexually Transmitted Disease Surveillance. Atlanta: U.S. Department of Health and Human Services; 2014. [cited 2014 April]. Available from:

Page Last Updated: March 31, 2014

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