Overview

Sexually transmitted diseases (STDs), or sexually transmitted infections (STIs), are generally acquired by sexual contact. The organisms that cause sexually transmitted diseases may pass from person to person in blood, semen, or vaginal and other bodily fluids.

Sometimes these infections can be transmitted nonsexually, such as from mother to infant during pregnancy or childbirth, or through blood transfusions or shared needles.

It's possible to contract sexually transmitted diseases from people who seem perfectly healthy, and who may not even be aware of the infection. STDs don't always cause symptoms, which is one of the reasons experts prefer the term "sexually transmitted infections" to "sexually transmitted diseases."

Symptoms

Sexually transmitted infections (STIs) can have a range of signs and symptoms, including no symptoms. That's why they may go unnoticed until complications occur or a partner is diagnosed. Signs and symptoms that might indicate an STI include:

  • Sores or bumps on the genitals or in the oral or rectal area
  • Painful or burning urination
  • Discharge from the penis
  • Unusual or odd-smelling vaginal discharge
  • Unusual vaginal bleeding
  • Pain during sex
  • Sore, swollen lymph nodes, particularly in the groin but sometimes more widespread
  • Lower abdominal pain
  • Fever
  • Rash over the trunk, hands or feet

Signs and symptoms may appear a few days after exposure, or it may take years before you have any noticeable problems, depending on the organism.

When to see a doctor

See a doctor immediately if:

  • You are sexually active and may have been exposed to an STI
  • You have signs and symptoms of an STI

Make an appointment with a doctor:

  • When you consider becoming sexually active or when you're 21 — whichever comes first
  • Before you start having sex with a new partner

Causes

Sexually transmitted infections can be caused by:

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

Sexual activity plays a role in spreading many other infectious agents, although it's possible to be infected without sexual contact. Examples include the hepatitis A, B and C viruses, shigella, and Giardia intestinalis.

Risk factors

Anyone who is sexually active risks exposure to a sexually transmitted infection to some degree. Factors that may increase that risk include:

  • Having unprotected sex. Vaginal or anal penetration by an infected partner who isn't wearing a latex condom significantly increases the risk of getting an STI. Improper or inconsistent use of condoms can also increase your risk.

    Oral sex may be less risky, but infections can still be transmitted without a latex condom or dental dam. Dental dams — thin, square pieces of rubber made with latex or silicone — prevent skin-to-skin contact.

  • Having sexual contact with multiple partners. The more people you have sexual contact with, the greater your risk. This is true for concurrent partners as well as monogamous consecutive relationships.
  • Having a history of STIs. Having one STI makes it much easier for another STI to take hold.
  • Anyone forced to have sexual intercourse or sexual activity. Dealing with rape or assault can be difficult, but it's important to be seen as soon as possible. Screening, treatment and emotional support can be offered.
  • Abusing alcohol or using recreational drugs. Substance abuse can inhibit your judgment, making you more willing to participate in risky behaviors.
  • Injecting drugs. Needle sharing spreads many serious infections, including HIV, hepatitis B and hepatitis C.
  • Being young. Half of STIs occur in people between the ages of 15 and 24.
  • Men who request prescriptions for drugs to treat erectile dysfunction. Men who ask their doctors for prescriptions for certain drugs — such as sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) — have higher rates of STIs. Be sure you are up to date on safe sex practices if you ask your doctor for one of these medications.

Transmission from mother to infant

Certain STIs — such as gonorrhea, chlamydia, HIV and syphilis — can be passed from an infected mother to her child during pregnancy or delivery. STIs in infants can cause serious problems and may be fatal. All pregnant women should be screened for these infections and treated.

Complications

Because many people in the early stages of an STI experience no symptoms, screening for STIs is important in preventing complications.

Possible complications include:

  • Pelvic pain
  • Pregnancy complications
  • Eye inflammation
  • Arthritis
  • Pelvic inflammatory disease
  • Infertility
  • Heart disease
  • Certain cancers, such as HPV-associated cervical and rectal cancers

Prevention

There are several ways to avoid or reduce your risk of sexually transmitted infections.

  • Abstain. The most effective way to avoid STIs is to abstain from sex.
  • Stay with one uninfected partner. Another reliable way of avoiding STIs is to stay in a long-term mutually monogamous relationship with a partner who isn't infected.
  • Wait and verify. Avoid vaginal and anal intercourse with new partners until you have both been tested for STIs. Oral sex is less risky, but use a latex condom or dental dam — a thin, square piece of rubber made with latex or silicone — to prevent direct contact between the oral and genital mucous membranes. Keep in mind that no good screening test exists for genital herpes for either sex, and human papillomavirus (HPV) screening isn't available for men.
  • Get vaccinated. Getting vaccinated early, before sexual exposure, is also effective in preventing certain types of STIs. Vaccines are available to prevent human papillomavirus (HPV), hepatitis A and hepatitis B.

    The Centers for Disease Control and Prevention (CDC) recommends the HPV vaccine for girls and boys ages 11 and 12. If not fully vaccinated at ages 11 and 12, the CDC recommends that girls and women through age 26 and boys and men through age 26 receive the vaccine.

    The hepatitis B vaccine is usually given to newborns, and the hepatitis A vaccine is recommended for 1-year-olds. Both vaccines are recommended for people who aren't already immune to these diseases and for those who are at increased risk of infection, such as men who have sex with men and IV drug users.

  • Use condoms and dental dams consistently and correctly. Use a new latex condom or dental dam for each sex act, whether oral, vaginal or anal. Never use an oil-based lubricant, such as petroleum jelly, with a latex condom or dental dam.

    Condoms made from natural membranes are not recommended because they're not as effective at preventing STIs. Keep in mind that while condoms reduce your risk of exposure to most STIs, they provide a lesser degree of protection for STIs involving exposed genital sores, such as human papillomavirus (HPV) or herpes. Also, nonbarrier forms of contraception, such as oral contraceptives or intrauterine devices, don't protect against STIs.

  • Don't drink alcohol excessively or use drugs. If you're under the influence, you're more likely to take sexual risks.
  • Communicate. Before any serious sexual contact, communicate with your partner about practicing safer sex. Reach an explicit agreement about what activities will and won't be OK.
  • Consider male circumcision. There's evidence that male circumcision can help reduce a man's risk of acquiring HIV from an infected woman (heterosexual transmission) by as much as 60 percent. Male circumcision may also help prevent transmission of genital HPV and genital herpes.
  • Consider the drug Truvada. In July 2012, the Food and Drug Administration approved the use of the combination drug emtricitabine-tenofovir (Truvada) to reduce the risk of sexually transmitted HIV infection in those who are at high risk. Truvada is also used as an HIV treatment along with other medications.

    When used to help prevent HIV infection, Truvada is only appropriate if your doctor is certain you don't already have HIV infection.

    Your doctor should also test for hepatitis B infection. If you don't have hepatitis B, your doctor may recommend the hepatitis B vaccine if you haven't had it yet. If you have hepatitis B, your doctor should test your kidney function before prescribing Truvada.

    Truvada must be taken daily, exactly as prescribed, and you'll need follow-up HIV and kidney function testing every few months. Truvada should only be used along with other prevention strategies such as condom use every time you have sex.