Overview

Sexually transmitted diseases (STDs) — or sexually transmitted infections (STIs) — are generally acquired by sexual contact. The bacteria, viruses or parasites 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 mothers to their infants during pregnancy or childbirth, or through blood transfusions or shared needles.

STIs don't always cause symptoms. It's possible to contract sexually transmitted infections from people who seem perfectly healthy and may not even know they have an infection.

Symptoms

STDs or 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 odorous 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. However, it may take years before you have any noticeable problems, depending on the organism causing the STI.

Causes

STDs or STIs can be caused by:

• Bacteria-: Gonorrhea, syphilis and chlamydia are examples of STIs that are caused by bacteria.
• Parasites-: Trichomoniasis is an STI caused by a parasite.
• Viruses-: STIs causes by viruses include HPV, genital herpes and HIV.

Other kinds of infections — hepatitis A, B and C viruses, shigella infection and giardia infection — can be spread through sexual activity, but it's possible to be infected without sexual contact.

Risk factors

Anyone who is sexually active risks some degree of exposure to an STD or STI. 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 risk. Oral sex may be less risky, but infections can still be transmitted without a latex condom or a dental dam — a thin, square piece of rubber made with latex or silicone.
• Having sexual contact with multiple partners-: The more people you have sexual contact with, the greater your risk.
• Having a history of STIs-: Having one STI makes it much easier for another STI to take hold.
• Being forced to engage in sexual activity-: Dealing with rape or assault is difficult, but it's important to see a doctor as soon as possible to receive screening, treatment and emotional support.
• Misuse of alcohol or use of recreational drugs-: Substance misuse 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 the new STIs occur in people between the ages of 15 and 24.