Sexually Transmitted Diseases (STDs)

Medically Reviewed by Zilpah Sheikh, MD on October 14, 2024
Written by Stephanie Langmaid
5 min read

STDs are sexually transmitted diseases. This means they are most often, but not exclusively, spread by sexual contact.

STDs used to be called venereal diseases (VD). Doctors more often use the term sexually transmitted infections (STI). They're among the most common contagious diseases. According to the CDC, 25 million new cases are reported in the U.S. each year.

STDs are serious illnesses that need treatment. By educating yourself about them, you can learn ways to protect yourself.

Dozens of infections can be spread through vaginal, anal, or oral sex. Among the most common are:

STDs are caused by germs and other organisms that hide in body fluids such as semen, blood, vaginal secretions, and sometimes saliva. These include:

  • Bacteria (chlamydia, gonorrhea, syphilis)
  • Viruses (HIV, genital herpes, HPV)
  • Parasites (trichomoniasis)

Most of the time, they're spread through sexual contact. But you can also get some STDs from skin contact, by sharing personal items such as toothbrushes or razors with someone who has one, or by contact with damp objects such as towels and wet clothing. Some viruses can also be spread through infected blood.

You're at a higher risk for an STI if you:

  • Have more than one sex partner
  • Don't use a condom during sex
  • Have had an STI before
  • Share needles when injecting intravenous drugs

Your symptoms will depend on which infection you have. Sometimes, STDs don't cause symptoms at all until you develop complications. When they do, the most common signs are:

  • Pain or burning when you pee
  • Discharge from your penis or vagina 
  • Skin lesions, such as sores, warts, or a rash

There are many other possible symptoms, including:

  • Bleeding
  • Pain in your pelvis, abdomen, or testicles
  • Fever
  • Fatigue
  • Nausea, vomiting, or diarrhea
  • Itching
  • Swollen lymph nodes
  • Weight loss

See your doctor to get tested if you have symptoms, or if you know you've been exposed. They will likely examine you for signs such as sores or a rash, and you may have lab tests of your:

  • Blood
  • Urine
  • Fluid from sores
  • Genital discharge

Because STDs often don't show symptoms, routine testing is important for people who are sexually active. If you know you have one, you can get treated before serious problems develop. You can also take steps to avoid spreading it to others.

Most screening tests use a sample of your blood, saliva, or urine. The only FDA-approved way to test for HPV is by taking a sample of cells from your cervix.

Screening recommendations are different depending on your level of risk. But in general, it's a good idea to test before you start a new sexual relationship. If you're at high risk, you should get tested every year.

Some kinds of STDs can be cured. Others are lifelong conditions that you manage through medications. Your treatment depends on what kind of infection you have.

Antibiotics. These drugs treat STDs caused by bacteria, including chlamydia and gonorrhea. They also work against the parasite that causes trichomoniasis. Usually, antibiotics will cure these STDs, although it's possible to be reinfected.

Antivirals. For infections caused by a virus, including genital herpes and HIV, these drugs can lessen symptoms and prevent flare-ups. But the virus stays in your body. 

Genital warts can be removed with a topical medication or a procedure such as freezing or surgery.

You can take several steps to lower your risk of getting an STD. Some involve choices you make about your sex life. For example:

  • Ask a new partner to get tested before you have sex.
  • Use a condom or dental dam every time you have sex.
  • Don't have sex when your judgment may be impaired, like if you've been drinking or using drugs.
  • Get tested regularly.

Other ways to protect yourself include:

Vaccines. Vaccines can prevent infection from hepatitis B and many types of HPV. They're part of the routine immunization schedule recommended for children in the U.S. Adults who didn't get the HepB vaccine as children can get it in either a two- or three-dose series. The HPV vaccine isn't recommended if you're over age 26, but talk to your doctor if you're concerned about your risk.

Medication. PrEP, which stands for pre-exposure prophylaxis, is a type of daily drug therapy that can prevent HIV infection. It's approved for people at very high risk who are negative for the virus.

You may also be able to prevent infection with chlamydia, gonorrhea, or syphilis if you get a dose of an antibiotic within a day or so of being exposed.

Circumcision. For men or those assigned male at birth, being circumcised can lower your risk of getting HIV and can reduce the spread of HPV and genital herpes.

You may not realize you have certain STDs until you have damage to your reproductive system or other organs. Untreated STDs can cause:

  • Infertility
  • Pregnancy complications
  • Vision damage
  • Heart disease
  • Increased cancer risk
  • Other infections

Pelvic inflammatory disease (PID) is a complication of gonorrhea and chlamydia that can affect women and people assigned female at birth. The infection spreads through your reproductive system, causing inflammation, pain, and scarring.

Having an STD while you're pregnant can cause problems for you and your baby. They put you at risk for: 

  • Miscarriage
  • Infection or inflammation inside your uterus
  • Preterm labor
  • Stillbirth

Risks to your baby include:

  • Low birth weight
  • Infections
  • Blindness
  • Brain damage
  • Death

Both syphilis and HIV can pass through your placenta to a fetus while it's in your uterus. During delivery, your baby can be infected with gonorrhea, chlamydia, HIV, hepatitis B, and genital herpes. Breastfeeding can also pass on HIV to your baby — as well as syphilis or herpes if you have a sore on your breast.

The CDC recommends you get tested for chlamydia, gonorrhea, hepatitis, HIV, and syphilis at some point in your pregnancy, so you can get treatment and take precautions during delivery.

The decision to tell your sex partners that you've tested positive for an STD is an ethical one. Doing so allows them to get treatment and so they don't spread it to others or even reinfect you.

Your legal requirements are different. Most state laws related to STDs address HIV specifically. According to the CDC, 34 states make it a crime to expose someone else to HIV. In 13 states, you have to tell your sex partners if you know you're HIV-positive.

Sexually transmitted diseases are infections that are usually spread through sexual contact. Some, which are caused by bacteria, can be cured. Others that are caused by viruses remain in your body but can be managed with medications. It's important for people who are sexually active to get tested. STDs don't always cause symptoms, and they can cause serious complications if not treated.

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