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Common STDs and the Organisms That Cause Them

The following information is from the Institute of Medicine Report, "The Hidden Epidemic: Confronting Sexually Transmitted Diseases, 1996;" the National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIAID), Office of Communications fact sheets, 1998; and the CDC fact sheet, "The Challenge of STD Prevention in the United States, 1996."

Overview Return to top

Sexually transmitted diseases (STDs) affect men and women of all backgrounds and economic levels. STDs are most prevalent among teens and young adults with nearly two-thirds of all STDs occurring in people under age 25. Some contributing factors in the rise of STDs include the facts that young people have become sexually active earlier, divorce is more common, and sexually active people are more likely to have multiple sex partners.

A lot of STDs initially cause no symptoms, especially in women. Symptoms, when they do develop, may be confused with those of other diseases that are not transmitted through sexual contact. STDs can still be transmitted person to person even if they do not show symptoms. Also, health problems caused by STDs tend to be more severe for women than for men.

Click on the images to view the larger version of each.

Disease: Acquired Immune Deficiency Syndrome (AIDS) Return to top
Organism: Human Immunodeficiency Virus (HIV)

AIDS (acquired immunodeficiency syndrome) was first reported in the United States in 1981. It is caused by the human immunodeficiency virus (HIV), a virus that destroys the body's ability to fight off infection. An estimated 900,000 people in the United States are currently infected with HIV. 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 sexual activity and by sharing needles used to inject intravenous drugs. If you have any questions about HIV infection or AIDS, you can call the CDC National STD and AIDS Hotline confidential toll-free number: 1-800-342-AIDS.

Disease: Chancroid Return to top
Organism: Hemophilus Ducreyi

Chancroid ("shan-kroid") is an important bacterial infection caused by Haemophilus ducreyi, which is spread by sexual contact. Periodic outbreaks of chancroid have occurred in the United States, the last one being in the late 1980s. These outbreaks are usually seen in minority populations in the inner cities, especially in the southern and eastern portion of the country. Globally, this disease is common in sub-Saharan Africa among men who have frequent contact with prostitutes.

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

Disease: Chlamydia Return to top
Organism: Chlamydia Trachomatis

Chlamydial ("kla-mid-ee-uhl") infection is the most common bacterial sexually transmitted disease (STD) in the United States today. The U.S. Centers for Disease Control and Prevention estimates that more than 4 million new cases occur each year. The highest rates of chlamydial infection are in 15- to 19-year-old adolescents regardless of demographics or location. Pelvic inflammatory disease (PID), a serious complication of chlamydial infection, has emerged as a major cause of infertility among women of childbearing age. Chlamydial infection is caused by a bacterium, Chlamydia trachomatis, and 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. The annual cost of chlamydial infection is estimated to exceed $2 billion.

Disease: Genital Herpes Return to top
Organism: Herpes Simplex Virus (HSV)

Genital herpes is a contagious viral infection that affects an estimated one out of four (or 45 million) Americans. Doctors estimate that as many as 500,000 new cases may occur each year. The infection is caused by the herpes simplex virus (HSV). There are two types of HSV, and both can cause genital herpes. HSV type 1 most commonly causes sores on the lips (known as fever blisters or cold sores), but it can cause genital infections as well. HSV type 2 most often causes genital sores, but it also can infect the mouth.

Both HSV 1 and 2 can produce sores in and around the vaginal area, on the penis, around the anal opening, and on the buttocks or thighs. 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.

Genital herpes infection usually is acquired by sexual contact with someone who unknowingly is having an asymptomatic outbreak of herpes sores in the genital area. People with oral herpes can transmit the infection to the genital area of a partner during oral-genital sex. Herpes infections also can be transmitted by a person who is infected with HSV who has noticeable symptoms. The virus is spread only rarely, if at all, by contact with objects such as a toilet seat or hot tub.

Disease: Genital Warts Return to top
Organism: Human Papillomavirus (HPV)

HPV Image

Human papillomavirus (HPV) is one of the most common causes of sexually transmitted disease (STD) in the world. Experts estimate that as many as 24 million Americans are infected with HPV, and the frequency of infection and disease appears to be increasing. More than 60 types of HPV have been identified by scientists. Some types of the virus cause common skin warts. About one-third of the HPV types are spread through sexual contact and live only in genital tissue. 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.

Like many sexually transmitted organisms, HPV usually causes a silent infection, that is one that does not have visible symptoms. One study sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) reported that almost half of the women infected with HPV had no obvious symptoms. Because the viral infection persists, individuals may not be aware of their infection or the potential risk of transmission to others and of developing complications.

Disease: Gonorrhea Return to top
Organism: Neisseria Gonorrhoeae

Neisseria Gonorrhoeae Image

Approximately 400,000 cases of gonorrhea are reported to the U. S. Centers for Disease Control and Prevention (CDC) each year in this country. The most common symptoms of gonorrhea are a discharge from the vagina or penis and painful or difficult urination. The most common and serious complications occur in women and, as with chlamydial infection, these complications include PID, ectopic pregnancy, and infertility. Historically, penicillin has been used to treat gonorrhea, but in the last decade, four types of antibiotic resistance have emerged. New antibiotics or combinations of drugs must be used to treat these resistant strains.

Disease: Syphilis Return to top
Organism: Treponema Pallidum

Treponema Pallidum Image

The incidence of syphilis has increased and decreased dramatically in recent years, with more than 11,000 cases reported in 1996. The first symptoms of syphilis may go undetected because they are very mild and disappear spontaneously. The initial symptom is a chancre; it is usually a painless open sore that usually appears on the penis or around or in the vagina. It can also occur near the mouth, anus, or on the hands. If untreated, syphilis may go on to more advanced stages, including a transient rash and, eventually, serious involvement of the heart and central nervous system. The full course of the disease can take years. Penicillin remains the most effective drug to treat people with syphilis.

Disease: Viral Hepatitis Return to top
Organism: Hepatitis Virus (A, B, C & D)

Hepatitis B virus infection is an STD with severe complications including chronic hepatitis, cirrhosis, and liver carcinoma. Of approximately 200,000 new hepatitis B virus (HBV) infections in the U.S. each year, approximately half are transmitted through sexual intercourse. Preliminary data from a large U.S. multisite study indicate that approximately one third of persons with acute hepatitis B virus infections in 1995 had a history of another STD. In addition to hepatitis B, several other types of viral hepatitis can be transmitted sexually. Hepatitis A is a cause of acute hepatitis and less than 5 percent of infections are transmitted through fecal-oral contact during sexual intercourse, mostly among men who have sex with men. Hepatitis D (delta) virus is a virus that can be sexually transmitted but requires the presence of hepatitis B virus to replicate. Sexual transmission of hepatitis D virus occurs but is less efficiently transmitted through sexual intercourse compared to hepatitis B virus. Hepatitis C virus, the most common cause of non-A non-B hepatitis, causes chronic liver disease in most infected adults. The efficiency of sexual and perinatal transmission of this virus, however, is much less than that for HBV or the human immunodeficiency virus.

At present, there are no specific treatments for the acute symptoms of viral hepatitis. Doctors recommend bed rest, a healthy diet, and avoidance of alcoholic beverages. A genetically engineered form of a naturally occurring protein, interferon alpha, is used to treat people with chronic hepatitis C. Studies supported by the National Institutes of Health led to the approval of interferon alpha for the treatment of those with chronic HBV as well.

Other STDs Return to top

Other diseases that may be sexually transmitted include trichomoniasis, bacterial vaginosis, cytomegalovirus infections, scabies, and pubic lice. For information on these diseases and others, visit the sexually transmitted disease section of the National Institute of Allergy and Infectious Diseases (NIAID) Web site at http://www.niaid.nih.gov/publications/stds.htm.

STDs and Pregnancy Return to top

STDs in pregnant women are associated with a number of adverse outcomes, including spontaneous abortion and infection in the newborn. Low birth weight and prematurity appear to be associated with STDs, including chlamydial infection and trichomoniasis. Congenital or perinatal infection (infection that occurs around the time of birth) occurs in 30 to 70 percent of infants born to infected mothers, and complications may include pneumonia, eye infections, and permanent neurologic damage.

The Relationship between STDs and HIV Return to top

Syphilis, herpes simplex virus type 2, chancroid, and other infections that cause genital or rectal ulcers have been associated with HIV infection in several studies. Research suggests that such open sores in the genital area may increase the risk for acquiring HIV because they provide an entryway for the virus. Having one of these sexually transmitted diseases (STDs) does not necessarily mean that the infected person also has HIV infection. However, the continuance of risky behavior that led to STD infection may increase the likelihood of eventually becoming infected with HIV.

How to Prevent STDs Return to top

The best way to prevent sexually transmitted diseases (STDs) is to not have sexual relations. There are ways to reduce the risk of contracting an STD if you decide to be sexually active. Ask a new sex partner if he or she has an STD, has been exposed to one, or has any unexplained physical symptoms. Do not have sex if your partner has signs or symptoms of STDs, such as sores, rashes, or discharge from the genital area. Many common STDs have no symptoms but can still be transmitted to a sexual partner. If your partner has had sexual relations with someone else recently, they may have an STD, even if there are no symptoms. Therefore, do not have sex if you think your partner may have been exposed to an STD, even if they do not show any symptoms. Also use a condom correctly during sexual intercourse. Get regular checkups for STDs (even if you show no symptoms), and be familiar with the common symptoms. Most STDs are readily treated, and the earlier treatment is sought and sex partners are warned, the less likely the disease will do irreparable damage.

STD Prevention Efforts in the United States Return to top

Throughout the world, an estimated 333 million new cases of curable sexually transmitted diseases (STD) occur each year among adults. Despite the fact that a great deal of progress has been made in STD prevention over the past four decades, the United States (US) has the highest rates of STDs in the industrialized world. The rates of STDs are 50-100 times higher in the US than in other industrial nations, even though rates of gonorrhea and syphilis have recently been brought to historic lows. A recent CDC report stated that STDs account for more than 85% of the most common infectious diseases in the US. There are an estimated 15.3 million new cases of STDs in the US each year, 3 million of which occur in persons aged 13 to 19 years.

STDs disproportionately affect women, infants, young people, and minorities. In women, STDs can lead to pelvic inflammatory disease (PID), infertility, potentially fatal ectopic pregnancies, and cancer of the reproductive tract. STDs can result in irreparable lifetime damage, including blindness, bone deformities, mental retardation, and death for infants infected by their mothers during gestation or birth.

Additional Information Return to top

If you have personal issues concerning Sexually Transmitted Diseases (STDs) and wish to speak to an information specialist to discuss risk factors and how to prevent STD transmission, you may call the CDC National STD Hotline, Monday through Friday, 8 a.m. to 11 p.m. (ET) at:

  • 1-800-227-8922
  • 1-800-243-7889 TTY
  • 1-800-344-7432 Spanish

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