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Urology Care Foundation The Official Foundation of the American Urological Association


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Get the facts. And the help you need.

Sexually Transmitted Infections (STIs)

Sexually transmitted infections (STIs) are also commonly referred to as venereal disease, and are some of the most common diseases that you can get from another person through sexual contact. With more than 20 STIs in existence, they affect more than 110 million men and women in the United States. Luckily, most are treatable. How do you know if you might have one? What is the best treatment? The following information should help answer these questions.

What are sexually transmitted infections (STIs)?

STIs are infections that are normally passed from one person to another through sexual contact. They can be relatively harmless or they can be painful, irritating, debilitating and even life threatening.

What causes STIs?

Bacteria and viruses that thrive in warm, moist environments within the body cause STIs.

How do STIs spread?

Most STIs are spread through bodily fluid transfers during sexual activity. Sexual activity can be defined as vaginal, anal or oral sex. However, there are some STIs that are transmitted by contact with infected blood. For instance, a STI may pass between people who share infected needles, while another STI may be passed from an infected mother to her child during pregnancy, childbirth or nursing.

STIs cannot be transmitted through casual contact (e.g., shaking hands) or objects such as clothing or toilet seats.

What are the symptoms for STIs?

Often there are no symptoms. However, some symptoms that may be indicative of a STI are the following:

  • an unusual discharge or odor from the vagina
  • pain in the pelvic area – the area between the belly button and genitals
  • pain in the groin area – the area around the genitals
  • genital burning or itching
  • bleeding from the vagina that is not a regular period
  • pain deep inside the vagina during sexual intercourse
  • penile drip or discharge
  • sores, bumps or blisters near the genitals, rectum or mouth
  • burning and pain during urination or bowel movement
  • frequent urination

Who is at risk for STIs?

STIs can affect men and women of all backgrounds and economic levels. However, some research suggests that STIs may be most prevalent among teenagers and young adults since they are more likely to have multiple sex partners during their lifetime. Individuals who are using dirty needles when injecting intravenous drugs are also at risk.

How are STIs diagnosed?

Most STIs can be diagnosed through an examination by a doctor, a culture of the secretions from the vagina or penis, or a blood test.

What are the most common types of STIs and how are they treated?

Chlamydia: This is the most common of all bacterial STIs, with an estimated four to eight million new cases each year, and is transmitted through vaginal and anal sex. Sometimes, it goes undiagnosed since it frequently does not produce noticeable symptoms. If symptoms are present in men, they typically include painful urination or a discharge from the penis. Symptoms in women may include bleeding between periods, painful urination, vaginal discharge or mild pain in the lower abdomen. Once diagnosed, a person can be treated with an antibiotic.

Gonorrhea: Approximately 400,000 cases are reported each year in the United States. It is transmitted through vaginal, anal or oral sex. Like Chlamydia, this STI is often present without symptoms. However any symptoms would most likely involve penile or vaginal discharge and painful urination. Gonorrhea is treatable with antibiotics.

Syphilis: This is a potentially life-threatening, bacterial STI commonly transmitted through vaginal, anal or oral sex. However, it can also be spread by non-sexual contact if the sores caused by the syphilis come in contact with the broken skin of a non-infected individual. Usually, the first symptom is a painless open sore that frequently appears around the penis or vagina but can also appear near the mouth, anus or hands. To date, penicillin has been proven to be the most effective treatment. If syphilis remains untreated, it may progress to more advanced stages and may result in medical conditions like a stroke or meningitis.

Genital Herpes: This STI is caused by an infection with the Herpes Simplex Virus Type 2 (HSV-2) and spreads by direct skin-to-skin contact with the infected site during vaginal, anal or oral sex. Another strain of the virus, Herpes Simplex Type 1 (HSV-1) is most commonly spread by nonsexual contact and usually causes sores on the lips but it can also be transmitted through oral sex. There is no known cure for HSV but symptoms can be treated with antiviral drugs.

Acquired Immune Deficiency Syndrome (AIDS): AIDS results from an infection with the human immunodeficiency virus (HIV) and is an incurable and deadly STI. It attacks the body's immune system and is most commonly transmitted through vaginal, oral and anal sex. It may also be transmitted by blood through the sharing of infected needles or other sharp instruments that break the skin or from an infected mother to her child during pregnancy, childbirth or nursing. When first infected, some people experience no symptoms while others have flu-like symptoms. These symptoms usually disappear within one to four weeks and the virus can remain inactive for years. There is no known cure, but antiviral drugs can be used to prolong the life and health of an infected person.

Hepatitis B: This viral STI, also referred to as HBV, is a serious virus that attacks the liver. It can be transmitted through vaginal, oral and anal sex. It may also be transmitted by blood through the sharing of infected needles or other sharp instruments that break the skin. The Centers for Disease Control and Prevention (CDC) estimates that 120,000 new hepatitis B infections occur each year. About a third of the people with hepatitis B have no symptoms. However, when symptoms are present, they can include fever, headache, muscle aches, fatigue, loss of appetite, vomiting and diarrhea. Since hepatitis B attacks liver cells, it can lead to cirrhosis, liver cancer, liver failure and possibly death. Symptoms that indicate involvement of the liver include dark urine, abdominal pain and yellowing of the skin or whites of the eyes. There is no known cure for hepatitis B but there are medications available to treat chronic infection in some patients. A vaccine is now available and is the best protection.

Genital Warts: These warts are caused by the human papillomavirus (HPV) and are transmitted through vaginal, anal or oral sex. The results are painless, fleshy, cauliflower-like warts that grow on the penis and in and around the entrance of the vagina or anus. According to the CDC, there are approximately 360,000 new cases each year in the United States. There is no known cure but they can be treated by topical medications and can sometimes be removed with minor surgical procedures (e.g., chemicals, freezing, laser).

Trichomoniasis: This common bacterial STI, transmitted through sexual contact, mainly affects young, sexually active women. Sometimes there are no symptoms associated with this STI. However, in women, symptoms can include foul smelling or frothy, yellow-green vaginal discharge, vaginal itching or redness, pain during intercourse, lower abdominal discomfort and/or frequent urination. In men, symptoms can include discharge from the penis, frequent urination and/or painful urination. Trichomoniasis can be easily treated with antibiotics.

Frequently asked questions:

How can STIs be prevented?

The following behaviors and conditions can help decrease your risk for STIs:

  • avoid sexual contact with infected persons
  • have a mutually monogamous sexual relationship with an uninfected partner
  • limit your number of sexual partners throughout your lifetime
  • correctly and consistently use a condom
  • use clean needles if you are injecting intravenous drugs

Can STIs cause any other health problems?

Some STIs can spread into the uterus and fallopian tubes and may subsequently cause pelvic inflammatory disease, which is frequently linked to both infertility and ectopic pregnancy. STIs can also be passed from a mother to her baby before or during birth or through breastfeeding. There has also been some indication that the human papillomavirus (HPV) may cause cervical cancer.

What if I am pregnant?

If you are pregnant and have symptoms of a STI, you should contact your doctor immediately. STIs during pregnancy can put a baby at risk if not addressed quickly and properly.

Can I get a STI by open-mouth kissing?

Open-mouth kissing is considered a very low-risk activity for the transmission of STIs, particularly HIV. However, prolonged open-mouth kissing could damage the mouth or lips and allow HIV to pass from an infected person to a partner and then enter the body through cuts or sores in the mouth. Because of this possible risk, the CDC recommends that a person avoid open-mouth kissing with an infected partner.

Should I be checked for STIs?

If you are at risk for having an STI, if you have any symptoms or if you just have concerns, you should see a doctor. It is recommended that HIV, HBV and syphilis testing and perhaps cultures be performed periodically if you have unprotected sex with multiple partners.

Reviewed: January 2011

Last Updated: March 2013

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Sexually Transmitted Infections (STIs) Glossary
  • abdomen: Also referred to as the belly. It is the part of the body that contains all of the internal structures between the chest and the pelvis.

  • abdominal: in the abdomen, the cavity of this part of the body containing the stomach, intestines and bladder.

  • antibiotic: Drug that kills bacteria or prevents them from multiplying.

  • antiviral: Capable of eliminating or inactivating viruses.

  • anus: Opening at the end of the digestive tract where feces (stool) leave the body. The final two inches of the rectum.

  • bacteria: Single-celled microorganisms that can exist independently (free-living) or dependently upon another organism for life (parasite). They can cause infection and are usually treated with antibiotics.

  • bacterial: Of or pertaining to a bacteria.

  • bowel: Another word for intestines or colon.

  • bowel movement: The act of passing feces (stool) through the anus.

  • cancer: An abnormal growth that can invade nearby structures and spread to other parts of the body and may be a threat to life.

  • cervical: Relating to the neck or any part of the body that resembles a neck. In the context of reproduction, it refers to the neck of the uterus (the cervix) in the female.

  • chronic: Lasting a long time. Chronic diseases develop slowly. Chronic renal (kidney) failure may develop over many years and lead to end-stage renal (kidney) disease.

  • culture: Biological material grown under special conditions.

  • ectopic: Used to describe an organ or body part occurring in a position or form that is not usual.

  • fallopian tubes: There are two fallopian tubes, one on each side of the uterus. They transport an egg from the ovary to the uterus.

  • fertility: The ability to conceive and have children.

  • genitals: Sex organs, including the penis and testicles in men and the vagina and vulva in women.

  • groin: The area where the upper thigh meets the lower abdomen.

  • HPV: Also known as juman papillomavirus. A family of over 60 viruses responsible for causing warts.

  • HPV: Also known as human papilloma virus. One of the most common causes of sexually transmitted disease.

  • immune system: The body's system for protecting itself from viruses and bacteria or any "foreign" substances.

  • infection: A condition resulting from the presence of bacteria or other microorganisms.

  • infertility: The diminished ability or the inability to conceive and have offspring.

  • inflammatory: Characterized or caused by swelling, redness, heat and/or pain produced in an area of the body as a result of irritation, injury or infection.

  • intravenous: Also referred to as IV. Existing or occurring inside a vein.

  • ions: Electrically charged atoms.

  • IV: Also referred to as intravenous. Existing or occurring inside a vein.

  • laser: Device that utilizes the ability of certain substances to absorb electromagnetic energy and re-radiates as a highly focused beam of synchronized single wave-length radiation.

  • liver: A large, vital organ that secretes bile, stores and filters blood, and takes part in many metabolic functions, for example, the conversion of sugars into glycogen. The liver is reddish-brown, multilobed, and in humans is located in the upper right part of the abdominal cavity.

  • pelvic: Relating to, involving or located in or near the pelvis.

  • penis: The male organ used for urination and sex.

  • pregnancy: The condition of being pregnant.

  • rectum: The lower part of the large intestine, ending in the anal opening.

  • secretion: Process of producing a substance from the cells and fluids within a gland or organ and discharging it.

  • stage: Classification of the progress of a disease.

  • stent: With regard to treating ureteral stones, a tube inserted through the urethra and bladder and into the ureter. Stents are used to aid treatment in various ways, such as preventing stone fragments from blocking the flow of urine.

  • topical: Describes medication applied directly to the surface of the part of the body being treated.

  • urination: The passing of urine.

  • urine: Liquid waste product filtered from the blood by the kidneys, stored in the bladder and expelled from the body through the urethra by the act of urinating (voiding). About 96 percent of which is water and the rest waste products.

  • urology: Branch of medicine concerned with the urinary tract in males and females and with the genital tract and reproductive system of males.

  • uterus: A hallow, muscular organ in the pelvis cavity of females in which the embryo is nourished and develops before birth.

  • vagina: The tube in a woman's body that runs beside the urethra and connects the uterus (womb)to the outside of the body. Sometimes called the birth canal. Sexual intercourse, the outflow of blood during menstruation and the birth of a baby all take place through the vagina.

  • void: To urinate, empty the bladder.

Sexually Transmitted Infections (STIs) Anatomical Drawings

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