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Sexually Transmitted Disease (STD) Basics

What Is a Sexually Transmitted Infection?

The term sexually transmitted disease (STD) is used to refer to any illness that is passed from one person to another through vaginal, anal, or oral sex. An STD may also be referred to as a sexually transmitted infection (STI) or venereal disease (VD). This does not mean that sex is the only way that STDs can be transmitted. Depending on the STD, infection may also be transmitted through:

  • shared needles
  • breastfeeding
  • non-sexual skin-to-skin contact
  • shared bedding or towels

Types of Sexually Transmitted Infections

A large number of infections can be transmitted sexually. Some STDs carry obvious symptoms. Common STD symptoms include:

  • rashes
  • pain during sex or urination
  • abnormal discharge
  • sores, bumps, or blisters

However, many people with STDs have no symptoms. Some STDs often lie dormant for years. According to the Mayo Clinic, asymptomatic STDs are so common that many people with STDs have no idea they are infected. They may pass on an STD to one or more partners without knowing it. They may also suffer internal damage while the STD remains untreated.

According to the Centers for Disease Control and Prevention (CDC), STDs such as syphilis and HIV can have severe consequences if left untreated. Even common diseases such as gonorrhea and chlamydia can cause problems if undiagnosed for long periods of time. Potential long-term consequences of untreated STDs include:

  • infertility
  • certain types of cancer
  • serious, whole-body illness
  • death (rare)

The most common STDs are described below.


Herpes is the short name for the herpes simplex virus, or HSV. There are two types of herpes, both of which are usually transmitted sexually. HSV-2 primarily causes genital herpes. In the past, HSV-1 primarily caused oral herpes. However, due to transmission during oral sex, HSV-1 now also causes a large number of genital herpes cases.

The most common symptom of both herpes viruses is blistery sores. They generally crust over and heal within a few weeks. Generally the first herpes outbreak is the most painful. Outbreaks usually become less painful and frequent over time.

There is no cure for herpes. Medications are available that can help to control outbreaks and may decrease pain during an outbreak. The same medications can also make you less likely to transmit herpes to your sexual partner. However, HSV can be transmitted even when you have no symptoms.

Herpes can be very dangerous to newborns. It’s very important that prospective mothers and pregnant women are aware of their HSV status.


Gonorrhea is a common bacterial STD. It’s also known as "the clap."

Most people with gonorrhea have no symptoms. Symptoms, if present, may include itching around the genitals and a yellowish-green discharge.

According to the CDC, untreated, gonorrhea can cause:

  • premature labor
  • infertility
  • serious health problems in newborns

Gonorrhea is treated with antibiotics.


According to the CDC, chlamydia is the most commonly reported bacterial STD in the United States.

Most people with chlamydia have no symptoms. When symptoms are present, they are similar to those of gonorrhea. Left untreated, chlamydia can cause:

  • pelvic inflammatory disease (PID)
  • infertility
  • infant health problems, including blindness (rare)

Chlamydia can be treated with antibiotics.


Syphilis is another bacterial infection. It often goes unnoticed in the early stages. The main early symptom is a painless, round sore (chancre). This is different than a canker sore.

Later symptoms of syphilis include:

  • fatigue
  • low-grade fever
  • rash
  • muscle pain

If left untreated, late-stage syphilis can lead to:

  • peripheral nerve damage
  • brain damage
  • death

Fortunately, if caught early enough, syphilis is easily treated by antibiotics. Syphilis infection in a newborn can be fatal. All pregnant women should be screened for syphilis.

HPV (Human Papillomavirus)

HPV can cause a range of health issues, including:

  • genital warts
  • cervical cancer
  • oral cancer
  • penile cancer
  • rectal cancer
  • vulvar cancer

There is no cure for HPV. However, there is a vaccine available that can protect against some of the most dangerous, cancer causing strains of HPV.

Most HPV infections will not become cancerous. In fact, the majority of people will clear an HPV infection within two years.  However, HPV infection is nevertheless a serious concern. According to the American Cancer Society, two-thirds of cases of cervical cancer in the United States are caused by HPV-16 and HPV-18. These are the two strains of the virus that most commonly cause cancer.

HIV (Human Immunodeficiency Virus)

According to the Mayo Clinic, a person can carry HIV and not show any symptoms for 10 years or longer. However, left untreated, HIV can compromise your immune system and cause acquired immunodeficiency syndrome (AIDS).

There is no cure for HIV. However, current treatment options are effective. When treated early, people infected with HIV can live as long as people without HIV. 

Effective, early treatment requires testing. The CDC recommends that everyone between the ages of 13 and 64 be tested at least once for HIV. People at high risk for HIV should be tested once a year.

HIV testing is widely available. Free and confidential testing can be found in all major cities and many public health clinics. A government web tool for finding a local test site is available at

Other STDs

Other, less common, STDs include:

  • chancroid
  • lymphogranuloma venereum
  • molluscum contagiosum
  • pubic lice
  • scabies

Diagnosing Sexually Transmitted Infections

Most STDs cannot be diagnosed simply by the presence of symptoms. Tests are needed to determine if you have an STD and what STD you might have.

These days, most STDs can be diagnosed using a urine or blood test. In addition, swabs may be taken of sores to check for viruses. Urethral and vaginal swabs can also be used to diagnose STDs.

You can get tested for STD at your regular doctor’s office or at a clinic. Although home testing kits are available, they may not always be reliable. Use them with caution, and check to see if the FDA has approved them.

Internet STD testing is also an option. Like home kits, the quality of such testing varies.

It’s important to know that a Pap smear is not an STD test. A Pap smear checks for the presence of precancerous cells on the cervix. It may also be combined with an HPV test for some women. However, a negative Pap smear does not mean you don’t have other STDs. You must be tested for each STD separately.

Treating Sexually Transmitted Infections

Treatment for STDs varies depending on what STD you have. It’s very important that both you and your sexual partner be successfully treated for STDs before resuming your sexual relationship. Otherwise you can pass an infection back and forth between you. 

Bacterial STDs

Bacterial infections can usually be treated fairly easily with antibiotics. It’s important to take all your antibiotics as prescribed. You should continue taking them even if you feel better before they are finished. You should also return to your doctor if your symptoms do not go away with treatment or if they return.

Viral STDs

Viral infections usually have no cure. However, treatment is available for many of these viral infections. Treatment can be very effective at stopping the progression of HIV. Medications are also available to reduce the frequency and severity of herpes outbreaks. Furthermore, antiviral drugs may reduce the risk of transmitting an STD to your partner.

Other STDs

Some STDs are caused by neither viruses nor bacteria. Instead they’re caused by other small organisms. Examples of such STDs include:

  • pubic lice
  • scabies
  • trichomoniasis
  • hepatitis

These STDs are usually easily treatable with appropriate oral or topical medications.

Preventing Sexually Transmitted Infections

Abstinence is the only foolproof way to avoid contracting an STD. However, there are ways to make sexual contact safer. When used properly, condoms provide the best protection against STDs, and have the additional benefit of providing contraception.

Using latex condoms or other barriers for anal and oral sex can also reduce your STD risk. Numerous STDs can be spread during oral sex, including:

  • gonorrhea
  • herpes
  • HPV
  • syphilis

Condoms and other barriers are generally very effective at preventing STDs that spread through infected fluids. However, they can’t fully protect against STDs that spread from skin to skin. If the barrier does not cover infected skin, the STD can still be passed to your partner.

Hormonally based birth control options, such as the pill and the ring, do not protect you from STDs. Intrauterine devices (IUDs) also do not prevent STDs.

Before having sex with a new partner, it’s important to discuss your sexual history. In addition, you should both be screened for STDs before having sex. As STDs often have no symptoms, testing is the only way to know if you are infected.

When discussing STD test results, it’s important to ask a partner what STDs they have been tested for. Many people assume their doctors have screened them for STDs as part of regular care. However, that usually isn’t true. People need to ask for the specific STD tests that they want. Urine or blood tests are available for:

  • chlamydia
  • gonorrhea
  • herpes
  • HIV
  • syphilis
  • trichomoniasis

Regular STD screening is a good idea for anyone who is sexually active. It’s particularly important for those with multiple partners or new partners.

Eligible people should also consider getting vaccinated for HPV and hepatitis. 

Content licensed from:

Written by: the Healthline Editorial Team
Medically reviewed on: Sep 15, 2014: Kenneth R. Hirsch, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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