The microbes that cause sexually transmitted diseases are equal opportunity bugs. They don't care if you are white or black, rich or poor, educated or illiterate, happy or sad. If you're a warm body, you'll do. STD germs settle in an estimated 15 million Americans each year. Worldwide, they find 250 million new hosts a year.

These numbers reflect men and women, young and old. STD germs love everybody who loves, because they are spread by intimate body contact. The word "venereal," as in venereal disease, comes from the name of the Romans goddess of love, Venus.

Germs can, however, be biologically sexist in the damage they do. Women suffer more adverse consequences from STDs than do men because, generally, it is easier for an STD to be transferred from a man to a woman. More harm can be done to a woman's reproductive organs if an infection is left untreated—and, women's infections do, in fact, go untreated more often, since women are less likely to show symptoms of an STD. The absence of symptoms in the presence of an infection is known medically as being "asymptomatic."

Two-thirds of all STDs occur in people under the age of 25. This isn't necessarily because this age group is more vulnerable to STDs. It's simply that these people are more likely to expose themselves to the number one risk factor for STDs: having sex with multiple partners without adequate protection from germs.