Overview
A sexually transmitted disease (STD) is a disease caused by a pathogen (e.g., virus, bacterium, parasite, fungus) that is spread from person to person primarily through sexual contact. STDs can be painful, irritating, debilitating, and life threatening. More than twenty sexually transmitted diseases have been identified.
Incidence and Prevalence
STDs occur most commonly in sexually active teenagers and young adults, especially those with multiple sex partners. An estimated 200 to 400 million people worldwide are infected—representing men and women of all economic classes.
According to the U.S. Department of Health and Human Services, in the United States more than 13 million people are infected each year and more than 65 million have an incurable STD. Generally, STD incidence has declined in the United States over the past 15 years, although rates among certain populations, including men who have sex with men, have increased.
Characteristics
Most STDs cause relatively harmless disease, producing few or no symptoms. However, some produce persistent asymptomatic or minimally symptomatic disease (e.g., chlamydia). Some people carry the disease for days or weeks, while others carry the disease for longer periods, even for life. During this time, an infected individual, or carrier, can spread disease.
In persistent infection, the pathogen evades detection by the immune system and remains fairly inactive, causing no overt disease. This inactivity is called latency. However, certain triggers (e.g., stress, immune suppression, injury) can reactivate latent pathogens. In some cases, reactivated disease is asymptomatic (e.g., chlamydia); in others, overt (e.g., genital herpes); and in still others, severe and even fatal (e.g., HIV/AIDS).
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by Kotik on Sun Sep 19, 2004 5:04 pm 
nevermind
