Common Sexually Transmitted Diseases (STDs) You Should Know About

Sexually transmitted diseases 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. Or when they do, they often don't want to do so effectively.

What is an STD? 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 considered STDs. Some are not at all related to sex. Other diseases are sexually-associated. Sexually-associated diseases aren't transmitted during sex. However, they may be associated with sex. For example, urinary tract infections aren't usually sexually transmitted, but irritation during intercourse can lead to one. 

Here are some common STDs and sexually-associated diseases that should be on your radar screen.


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 one of the most common STDs is that most people who get chlamydia don't have symptoms for weeks, months, or even years. In other words, they're asymptomatic.

Despite the lack of symptoms, it's important to get screened and treated if you think you might have been exposed to chlamydia. If you don't, 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.


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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 120 cases for every 100,000 people... and that number has been going up for several years.

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.

Currently, one of the biggest concerns about gonorrhea is treating it. There is a growing problem of antibiotic-resistant gonorrhea. One day, gonorrhea may not be treatable at all. 


An electron microscopy image of two Treponema pallidum bacteria. T. pallidum is the bacterium that causes syphilis. Photo courtesy of CDC/Joyce Ayers (1969)

Syphilis is a common STD 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.That means it can be transmitted by oral sex as well as vaginal or anal intercourse. In fact, some scientists think that oral sex is responsible for the rise of syphilis in men who have sex with men. 

Because syphilis sores can appear on areas not covered by a condom, condoms only reduce the likelihood of transmission but don't 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.

Mycoplasma Genitalium

Gynecologist Visit. 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. Furthermore, MG, like gonorrhea and chlamydia, is starting to emerge as a major cause of cervicitis in women and nongonococcal urethritis in men.

Why did it take so long to recognize the importance of this now common STD? Most cases of M. genitalium don't cause symptoms. It was difficult to identify until new technology became available. There is still no diagnostic test of MG that is cleared by the FDA for use in the U.S.

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.


Two [i]Trichomonas vaginalis[/i] organisms. Photo courtesy of the CDC Parasite Image Library

Trichomoniasis is the most common curable STD, with infection more common in women than in men. 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, but they don't tend to have symptoms. Still, if you are a woman who has been diagnosed with the disease, make sure your partner gets treated. If your partner is a man, trich may not be affecting him much, but you don't want him giving it back to you. If your partner is a woman, you could be passing the disease to each other as well.

Human Papilloma Virus/HPV

HPV Vaccine
Joe Raedle /Getty Images News/Getty Image

HPV is quite possibly the most common STD. Older studies from before the HPV vaccine was available estimated that three-quarters of the sexually active population had HPV at some point during their lives and one-quarter of women were 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, and they're linked to more than just cervical cancer. Others cause genital warts, other warts, or no symptoms at all.

Although HPV is considered incurable, its symptoms can be treated, and many people resolve infections on their own. It is recommended that 11 to 12-year-olds get the HPV vaccine to protect young men and women from the four most common strains of the virus.


Scanning electron micrograph of HIV-1 budding from cultured lymphocyte. 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 (HAART), or combined anti-retroviral therapy (cART). Although these therapies cannot cure the disease, they can reduce the likelihood that infection will progress to AIDS. HIV is no longer a death sentence. Many people with the virus are living long and healthy lives.

Crabs/Pubic Lice

Skin reaction to a pubic lice infestation. 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 coarse-haired areas of the body, such as the armpits or the eyebrows. They are usually spread by sexual contact, although they also can occasionally 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. It also simply isn't true that you have to shave off all your pubic hair if you get infected.


Scabies Mite - Sarcoptes scabiei var. hominis. 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 in 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.


A transmitting electron micrograph of numerous herpes simplex virions. 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 percent effective since herpes is spread skin-to-skin.


A person with Jaundice caused by acute Hepatitis infection. You can see how the whites of his eyes are yellowed. Photo courtesy of CDC/Dr. Thomas F. Sellers/Emory University (1963)

There are several types of hepatitis. Although the different viruses are transmitted through various routes, they all cause damage to the liver. The type of hepatitis most often associated with sexual transmission is hepatitis B (HBV). However, hepatitis C can also be sexually transmitted.

Over time, chronic infection with hepatitis B can lead to scarring of the liver, cirrhosis, and liver cancer. Fortunately, there is a vaccine that can protect you against infection. Nevertheless, approximately 1.25 million people in the United States have chronic infection with HBV.


Haemophilus ducreyi - The bacteria that cause chancroid. CDC/ Dr. Mike Miller

Chancroid is a genital ulcer disease caused by the bacterium Haemophilus ducreyi. Although not commonly seen in the United States, in other parts of the world chancroid infections are a major risk factor for HIV.

The ulcers caused by chancroid are generally larger and more painful than those associated with syphilis, although the early signs may be mistaken for those of a syphilis infection.

Bacterial Vaginosis/BV

Clue cells are vaginal epithelial cells that are covered in bacteria. They are one way of diagnosing bacterial vaginosis. Photo Courtesy of the Public Health Image Library; CDC/M. Rein

Bacterial vaginosis is a condition where the healthy bacteria in a woman's vagina disappear and are replaced by different organisms. Symptoms include burning and itching around the vagina, white or gray discharge, and a strong fishy odor that is particularly noticeable after intercourse.

Some people question whether or not BV is an STD, but it is associated with having a new sex partner or multiple sex partners. You can take antibiotics to get rid of BV, but it frequently shows up again even after successful treatment. Infection can increase a woman's risk of HIV, pelvic inflammatory disease, and pre-term birth (babies born too early).

Nongonoccocal Urethritis (NGU)

Doctor with male patient. Image Source/Photodisc/Getty Images

Unlike most of the STDs mentioned in this overview, nongonoccocal urethritis is not caused by a specific bacterium or virus. Instead, it is defined as any type of urethritis that is not caused by gonorrhea. The two most common causes of NGU are chlamydia and Mycoplasma genitalium. Symptoms of NGU include burning when urinating and discharge from the head of the penis. However, as with many STDs, most cases of NGU are asymptomatic.

Molluscum Contagiosum

Molluscum Contagiosum
Ed Uthman/Wikimedia Commons via Flickr/CC-BY-2.0

Molluscum contagiosum is a skin disease that most often affects young children and adults who have weakened immune systems. It is transmitted by direct skin contact, and so among adults it also can be transmitted during sexual contact.


MRSA bacteria. Computer artwork of methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Science Photo Library - SCIEPRO/Brand X Pictures/Getty Images

MRSA, or methicillin-resistant Staphylococcus aureus, is not primarily thought of as a sexually transmitted disease, although new research suggests that it probably can be transmitted sexually. Although most cases of MRSA are acquired in ​the hospital or other medical settings, it can also be transmitted by direct skin-to-skin contact.

Lymphogranuloma Venereum

John Slater/Digital Vision/Getty Images

Lymphogranuloma venereum (LGV) is a sexually transmitted disease that used to be primarily thought of as affecting individuals the developing world. However, it is now on the rise worldwide. After an initial outbreak in men who have sex with men (MSM) in the Netherlands in 2003, LGV has been found in isolated groups of MSM across western Europe, North America, and Australia. Caused by a type of Chlamydia trachomatis, LGV is closely associated with HIV infection and, as with many other STDs, can actually increase the risk of HIV transmission and acquisition.


2015 Sexually Transmitted Diseases Treatment Guidelines. CDC.

Emerging Issues. CDC.

Sexually Transmitted Diseases (STDs) Data & Statistics. CDC.