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Top Sexually Transmitted Diseases (STDs) You Should Know About


Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

STDs are some of the most difficult diseases in the world to catch. You have to be up close and personal to spread them. Why, then, are STDs so common? Because people don't know how to treat, prevent, and avoid them.

An STD is any disease that is spread primarily by sexual contact. One partner transmits the disease-causing organism to the other partner during sex (oral/vaginal/anal/etc.). Not all diseases that affect the sex organs are STDs. Some are not at all connected with sex. Other diseases are simply sexually associated.

Here are some common STDs that should be on your radar screen.

1. Chlamydia

Chlamydia screening smear test
Chlamydia is the most common curable STD. It infects the cervix in women, and the penile urethra in men. Its most frequent symptoms are pain during sex, and discharge from the penis or vagina. However, the reason chlamydia is so common is that most people who get chlamydia don't have symptoms for weeks, months, or even years. Despite the lack of symptoms, it's important to get screened and treated if you think you might have been exposed to chlamydia, because it can do a lot of damage to your body in the long run. Want to avoid getting chlamydia? Latex condoms are effective at preventing the disease.

2. Gonorrhea

Photolink/Getty Images
Gonorrhea, otherwise known as "the clap," is another common bacterial STD. In general it infects the same organs as chlamydia, and has similar long-term effects. Symptoms of gonorrhea include burning when urinating and, in men, white, yellow, or green discharge from the penis. Just as with chlamydia, however, many people with gonorrhea don't have symptoms. This is why the CDC estimates that, in the United States alone, there are more than 700,000 new cases a year. Oh, and if you're one of those people who thinks that oral sex is safe sex (or isn't sex at all), you should know that gonorrhea can also infect the throat.

3. Syphilis

Photo courtesy of CDC/Joyce Ayers (1969)
Syphilis is a sexually transmitted disease with a notorious history. Caused by the bacterium Treponema pallidum, it can lead to serious complications if left untreated. Syphilis is transmitted by direct contact with syphilis sores, which can appear on the external genitals and the mouth, as well as in the vagina or rectum. Because these sores can appear on areas not covered by a condom, condoms only reduce the likelihood of transmission, but not eliminate it entirely. The small painless sores (chancres) of early syphilis may heal by themselves, but that doesn't mean the disease is gone -- it's just become more difficult to detect and treat.

4. Mycoplasma Genitalium

Angela Wyant/The Image Bank/Getty Images
In 2007, a prominent study of U.S. adolescents found that a little known STD, Mycoplasma genitalium had surpassed gonorrhea in prevalence. Most cases of M. genitalium don't cause symptoms and it had been difficult to identify until more recent technology became available. While the emerging research is still unclear, it is thought that MG is associated with serious long-term consequences, including infertility from pelvic inflammatory disease. MG, like gonorrhea and chlamydia, may emerge as a major cause of cervicitic in women, and nongonococcal urethritis in men.

5. Trichomoniasis

Photo courtesy of the CDC Parasite Image Library
Trichomoniasis is the most common STD in sexually active young women. Some women may mistake this infection for a yeast infection or bacterial vaginosis since the symptoms are similar: frothy discharge, strong vaginal odor, pain on intercourse, irritation and itching. Men can get trichomoniasis too, but they don't tend to have symptoms. If you are a young woman who has been diagnosed with the disease, make sure your partner gets treated. Trich may not be affecting him much, but you don't want him giving it back to you! And, if your partner is a woman, you could be passing the disease to each other as well.

6. Crabs/Pubic Lice

Photo courtesy of the CDC/Joe Miller
"Crabs" are a form of lice that live on the hair in the genital area and occasionally on other course-haired areas of the body, such as the armpits or the eyebrows. They are usually spread by sexual contact, although they also can be transmitted by infested linens and clothing. Symptoms include itching in the genital area and visible lice or eggs. You should know that crab lice are not the same as head lice, and that they almost never infest the hair on the head. And the rumor that you have to shave off all your pubic hair if you get infected? That simply isn't true.

7. Scabies

CDC/Joe Miller/Reed & Carnrick Pharmaceuticals
Scabies is a contagious skin disease that is not always sexually transmitted. Caused by the parasite Sarcoptes scabei, scabies causes an extremely itchy rash that gets worse at night. The rash is most often found on folds of skin, such as between the fingers, on the wrists and ankles, and in the genital area. Scabies is incredibly contagious, and the mite can live for days off the human body. It is not only spread by close personal contact, but by skin-to-skin contact in general, shared clothing, towels and bedding.

8. Human Papilloma Virus/HPV

Joe Raedle /Getty Images News/Getty Image
HPV is quite possibly the most common STD. One 1997 study estimated that three-quarters of the sexually active population has had HPV at some point during their lives, and a study released in 2007 found that one-quarter of women are infected at any given time. HPV may be known as "the cervical cancer virus," but only a few types of HPV are linked to cancer. Others cause genital warts, or no symptoms at all. Although HPV is considered incurable, its symptoms can be treated, and many people resolve infections on their own. Recently the government approved a new vaccine to protect young women from the four most common strains of the virus.


Photo Courtesy of the Public Health Image Library; C. Goldsmith
HIV is the virus associated with AIDS. It can only be transmitted by an exchange of bodily fluids -- including semen, vaginal secretions, breast milk and blood. It cannot be transmitted by casual contact. Currently, most people with HIV are treated with a combination of drugs known as highly active anti-retroviral therapy, or HAART. Although this cannot cure the disease, it can reduce the likelihood that it will progress to AIDS. HIV is no longer a death sentence: many people with the virus are living long and productive lives.

10. Herpes/HSV

Photo courtesy of CDC/Dr. Fred Murphy; Sylvia Whitfield (1975)
Herpes is another viral STD. It comes in two forms, HSV1 and HSV2. HSV1 is most often associated with cold sores, and HSV2 is most often associated with genital sores. However, it is possible to transmit herpes from the mouth to the genitals and vice versa. Herpes symptoms can be treated with anti-viral drugs, but the virus cannot be cured. People with the herpes virus need to know that they can transmit the virus even when they do not have any sores or other symptoms. Although using a condom can reduce the risk of herpes transmission, condoms are not 100% effective since herpes is spread skin-to-skin.
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