Facts About Sexually Transmitted Infections
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Facts About Sexually Transmitted Infections

What You Need to Know to Protect You and Your Family

So you know all about protecting yourself from sexually transmitted infections (STIs)? Just use a condom, right? Well, what you don’t know about STIs could hurt you!

Almost 15 million new cases of STIs are diagnosed in the United States each year—approximately one-fourth of them found in teenagers. Because many of these infections do not have symptoms, countless people may not know that they have an STI. Here are some facts about STIs:

STI 101

What Are Sexually Transmitted Infections (STIs)?

Sexually transmitted infections are infections caused by bacteria, viruses, or other organisms. The STIs caused by bacteria can be cured with antibiotics, while viruses cannot be cured (though the symptoms can be treated). Common STIs and their specific treatments and prevention strategies are listed below.

How Are STIs Transmitted?

STIs are usually spread through sexual contact, including vaginal, oral, and anal sex. The viruses and bacteria that cause STIs are normally carried in the semen, vaginal fluids, or blood. They enter the body through tiny tears or cuts in the mouth, anus, or genitals. STIs can be passed from person-to-person even without having sexual intercourse. For instance, someone can contract herpes or genital warts through skin-to-skin contact with an infected sore or area. Intercourse during menstruation increases the chance of becoming infected with certain organisms.

How Can STIs Be Prevented?

There is only one 100% effective way to be sure that you stay STI-free—no sex or intimate physical contact with anyone. If you are sexually active, you can reduce your chances of getting an STI by avoiding high-risk behaviors like unprotected sex, multiple sex partners, and intravenous drug use. A latex condom (preferably accompanied by a spermicide) should always be used when having sex.

Symptoms of STIs

When to See a Physician Right Away

  • Abnormal or smelly discharges, pus, or odors from the vagina, penis, or rectum
  • Boils, blisters, buboes, chancres, polyps, growths, sores, or warts
  • Burning sensations
  • Bleeding
  • Irritation, tenderness, swelling, rashes, itching
  • Painful intercourse, other pains
  • Vaginal yeast infections, cervicitis, urine changes
  • Ulcers
  • After sexual contact with someone who has a known sexually transmitted disease

Other Possible Symptoms of an STI

  • Weight loss that is constant, rapid, or unexplained
  • Coatings of the mouth, throat, or vagina
  • Abdominal pain, muscular pain, aching joints, general weakness, feeling run down
  • Coughs, chills, night sweats, or fevers
  • Bowel problems, diarrhea, vomiting, appetite loss, nausea
  • Vaginitis
  • Headaches, lightheadedness, vision loss, hearing loss, mental disorders
  • Discolored skin, hair loss, jaundice
  • Swollen glands, sore throat, fatigue
  • Growths

Some Common STIs

  • Bacterial Vaginosis—Bacterial vaginosis (BV) is caused by a change in the balance of different kinds of bacteria in the vagina. When there are symptoms, they often appear as a form of vaginitis—an irritation of the vagina often associated with a vaginal discharge. BV is not always sexually transmitted, though sexual activity increases the risk.
    • Treatment: Antimicrobial creams applied to the vagina
    • Protection: Condoms offer good protection against BV
  • ChlamydiaWhen diagnosed, chlamydia can be easily treated and cured. Untreated, chlamydia can cause severe, costly reproductive and other health problems. It can cause bladder infections and serious pelvic inflammatory disease (PID), ectopic pregnancy, and sterility in both men and women. It is the most frequently reported infectious disease in the United States and as many as 1 in 10 adolescent girls tested for chlamydia is infected.
    • Treatment: Both partners can be treated successfully with antibiotics
    • Protection: Condoms offer very good protection against chlamydia
  • Cytomegalovirus (CMV)—CMV is a member of the herpesvirus group. Once infected, a person can carry the virus for life, even though they may never have active symptoms. Each year, CMV causes permanent disability, including hearing loss and mental retardation, for 4,000-7,000 babies. This virus is also very dangerous for people with weakened immune systems, and can cause blindness and mental disorders.
    • Treatment: There is no cure, though symptoms may be helped with some medications. Vaccines are still being researched and developed.
    • Protection: Condoms can provide protection against CMV during vaginal, anal, and oral intercourse, but kissing and other intimate touching can spread the virus.
  • Gonorrhea—Gonorrhea is caused by the bacterium Neisseria gonorrhoeae , which is transmitted during vaginal, oral, or anal sexual intercourse. It can cause sterility, arthritis, and heart problems in both men and women. More than 600,000 new cases of gonorrhea are reported every year in the US.
    • Treatment: Both partners can be treated successfully with antibiotics. People with gonorrhea often have other STIs like chlamydia. Infections must be treated at the same time.
    • Protection: Condoms offer very good protection against gonorrhea.
  • Hepatitis B Virus (HBV)—About 1.25 million people in the US have chronic HBV infection. Each year it is estimated that 80,000 people, mostly young adults, get infected with HBV and 4,000-5,000 people die from chronic hepatitis B in the United States. The virus can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.
    • Treatment: There is no cure, but in most cases the infection clears within 4-8 weeks. If a chronic infection develops, treatments are available for suppressing the virus, but some people remain contagious for the rest of their lives.
    • Protection: Condoms offer some protection against HBV during vaginal, anal, and oral intercourse, but the virus can be passed through kissing and other intimate touching. Hepatitis B vaccine can prevent this disease and is the first anticancer vaccine because it can prevent a form of liver cancer.
  • Herpes Simplex Virus (HSV)—Both herpes simplex virus-1 and herpes simplex virus-2 can be sexually transmitted (HSV-1 is most often associated with cold sores and fever blisters). One million new cases are diagnosed every year, and like many other viruses, the HSV remains in the body for life. HSV can cause miscarriage or stillbirth during pregnancy. If active herpes infections are present during childbirth, newborn infants may suffer serious health problems, including developmental disabilities and, rarely, death.
    • Treatment: There is no cure, though symptoms and recurrences may be helped with medications like valacyclovir, acyclovir, and famciclovir.
    • Protection: Partners should refrain from sexual contact from the time they know the blisters are going to recur until after the scabs have completely fallen off the healed sores. Condoms offer some protection against the virus between outbreaks.
  • Human Immunodeficiency Virus (HIV)—HIV is a virus that weakens the body’s ability to fight off infections and can cause acquired immune deficiency syndrome (AIDS)—the last stage of HIV infection. This compromised immune system can make a carrier more susceptible to pneumonia, cancer, and a variety of other infections. Currently, almost a million people in the United States are infected with HIV. Like many other viruses, HIV remains in the body for life.
    • Treatment: There is no cure, though HIV infection and many AIDS-related conditions can be managed to some extent with a variety of treatments. AIDS is no longer fatal to everyone who has it.
    • Protection: Condoms offer very good protection against HIV.
  • Human Papilloma Virus (HPV) & Genital Warts —HPV is a family of more than 100 extremely common viruses. Many types of HPV cause harmless skin warts, such as those on the fingers or feet. HPV is easily spread during oral, genital, or anal sex with an infected partner. Some of these viruses are associated with cancer of the cervix, vulva, or penis.
    • Treatment: There is no cure for HPV, though genital warts can be treated or removed in a number of ways including: topical medication, application of acid, standard or laser surgery, cryosurgery (freezing the wart with liquid nitrogen) and injection of interferon.
    • Protection: Recently, a vaccine called Gardasil™ was approved by the US Food and Drug Admistration to protect against HPV infection. The vaccine targets four strains of HPV, two of which cause 70% of all cervical cancers. Gardasil™ cannot treat an existing infection. Condoms may also offer some protection against genital HPVs, but the viruses may "shed" beyond the area protected by a condom.
  • Molluscum Contagiosum—Hundreds of thousands of cases of this virus are diagnosed every year, and it is often transmitted by nonsexual, intimate contact. Small, pinkish-white, waxy, round polyps grow in the genital area or on the thighs, and there is often a tiny depression in the middle of the growth. Molluscum contagiosum belongs to a family of viruses called poxviruses and it is generally spread by skin-to-skin contact. It can be sexually spread if growths are present in the genital area. It is not known to affect any internal organs or cause cancer.
    • Treatment: Growths may be removed with chemicals, electrical current, or freezing.
    • Protection: Condoms may offer some protection against Molluscum contagiosum, but the virus may "shed" beyond the area protected by the condom.
  • Pelvic Inflammatory Disease (PID)—PID is a progressive infection that harms a woman's reproductive system. It can lead to sterility, ectopic pregnancy, and chronic pain. PID is often caused by sexually transmitted infections like gonorrhea and chlamydia. More than 750,000 new cases of PID are diagnosed every year in the US, with possibly millions more undiagnosed.
    • Treatment: Antibiotics, bed rest, and sexual abstinence. Surgery may be required to remove abscesses or scar tissue, or to repair or remove reproductive organs.
    • Protection: Condoms offer very good protection against infections commonly associated with PID.
  • Pubic Lice—Every year, millions of people treat themselves for pubic lice. These tiny parasitic insects are also called "crabs" or "cooties" and are generally found in the genital area of humans. Pubic lice are usually spread through sexual contact. Rarely, infestation can be spread through contact with an infested person's bed linens, towels, or clothes.
    • Treatment: Over-the-counter medication is available to treat anyone who may have been exposed to pubic lice. All bedding, towels, and clothing that may have been exposed should be thoroughly washed or dry cleaned, and the home should be vacuumed.
    • Protection: Limiting the number of intimate and sexual contacts can help.
  • Scabies—Scabies is an infestation of the skin with the microscopic mite Sarcoptes scabei. It is usually sexually transmitted. However, school children often pass it to one another through casual contact.
    • Treatment: Over-the-counter medication is available to treat anyone who may have been exposed to scabies. All bedding, towels, and clothing that may have been exposed should be thoroughly washed or dry cleaned, and the home should be vacuumed.
    • Protection: Limiting the number of intimate and sexual contacts can help. Also, avoid close physical contact or sharing clothing, towels, or bedding with anyone who has either scabies or an undiagnosed itchy rash—especially a rash that has been present for over a week.
  • Syphilis—This complex sexually transmitted disease (STD) is caused by the bacterium Treponema pallidum. Many of the signs and symptoms of syphilis are indistinguishable from those of other diseases. It is passed from person-to- person through direct contact with syphilis sores, which occur mainly on the external genitals, vagina, anus, or in the rectum. Sores also can occur on the lips and in the mouth. Syphilis cannot be spread by toilet seats, door knobs, swimming pools, hot tubs, bath tubs, shared clothing, or eating utensils. If left untreated, the syphilis can remain in the body for life and lead to disfigurement, neurologic disorder, or death.
    • Treatment: Antibiotics are successful for both partners, but damage caused by the disease in the later phases cannot be undone.
    • Protection: Condoms offer very good protection during vaginal, anal, and oral intercourse.
  • Trichomoniasis—"Trich" is a condition caused by a protozoan—a microscopic, one-cell animal. It is a common cause of vaginal infections. Up to five million Americans develop trichomoniasis every year. It is spread through vaginal intercourse.
    • Treatment: Drugs called 5-notroimidazoles are successful for both men and women.
    • Protection: Condoms offer very good protection against trich. Spermicide offers some protection.
  • Urinary Tract Infections (UTI)—UTIs are caused by bacteria that have spread from the rectum to the vagina or penis, and then to the urethra and bladder. They may be transmitted by any kind of sex play that brings fecal material into contact with the vagina and urethra. Unprotected anal intercourse is a very high-risk behavior for urinary tract infection. Severe cases, left untreated, may cause kidney infection.
    • Treatment: UTIs can be treated with antibiotics and other medications may decrease the symptoms.
    • Protection: Condoms and avoiding sexual positions that seem to trigger UITs can help.


Centers for Disease Control and Prevention

Planned Parenthood Federation of America

National Library of Medicine


Sex Information and Education Council of Canada



American College of Obstetricians and Gynecologists website. Available at: http://www.acog.org/.

Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/std/.

Komaroff AL. Harvard Medical School Family Health Guide. New York, NY: Simon & Schuster; 1999.

Ronco G, Segnan N, Giorgi-Rossi P, et al, for the New Technologies for Cervical Cancer Working Group. Human papillomavirus testing and liquid-based cytology: results at recruitment from the new technologies for cervical cancer randomized controlled trial. J Natl Cancer Inst. 2006;98:765-774.

Last reviewed July 2008 by Jill Landis, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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