STDs are among the most common infectious diseases in the world today.

There are over 20 types, affecting more than 13 million men and women in the United States alone each year, and the incidence is on the rise.

Some of the most common STDs include chlamydial infection, genital herpes, genital warts, gonorrhea, HIV (human immunodeficiency virus, the microorganism that causes AIDS), and syphilis.

General Signs and Symptoms
STDs often occur without symptoms, particularly in women. However, STDs may be accompanied by the following signs and symptoms:

• Itching
• Discharge
• Pustules (pus-containing blisters)
• Genital lesions including ulcers, blisters, rashes, and warts; ulcers may be painful
• Abdominal pain
• Rectal infection and inflammation of the rectum
• Fever
• Muscle pain
• Painful urination
• Swollen lymph glands in the groin
  

What Causes It?
STDs are caused by microbial agents and spread primarily (but not exclusively) through sexual contact. Some STDs can also be passed from a mother to her baby during delivery and through breastfeeding while infected. Others may be passed by sharing infected needles.

Some of the most common STDs and the microorganisms that cause them are listed below.

Chlamydial infection—Chlamydia trachomatis
Genital herpes—herpes simplex virus (HSV)
Genital warts—human papillomavirus (HPV)
Gonorrhea—Neisseria gonorrhoeae

Who's Most At Risk?
People with the following conditions or characteristics are at risk for developing STDs.

• Having a sexual partner with an STD; again, in many cases, an STD may be present without symptoms
• Having many sexual partners, or a partner who has many sexual partners
• Having sex without the use of condoms or other protective devices
• Having one STD increases the likelihood of contracting another
• Adolescents are at highest risk for acquiring an STD for the first time
• Living under stress from poverty, poor nutrition, or poor or absent healthcare
• Practicing anal intercourse increases risk for HIV, gonorrhea, and syphilis
• Having a weakened immune system
• Using intravenous drugs
• Using spermicidal foams and jellies does not protect against STDs and may, in some cases, even promote contraction of certain STDs, including HIV

Specific STD Information

Chlamydia

Genital herpes

Genital warts

Gonorrhea

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