More than 20 STDs have now been identified, and affect more than 13 million men and women in this country each year. STDs affect men and women of all backgrounds and economic levels, but are most prevalent among teenagers and young adults, with nearly two-thirds of all STDs occurring in people younger than age 25. The incidence of STDs continues to rise. The suggested reason is that sexually active people today are more likely to have multiple sex partners during their lives. Even when an STD causes no symptoms, it is still contagious to a partner during intercourse.
Problems associated with or caused by STDs are usually more severe and more frequent in women.
The latter can be fatal. While some infections of the newborn may be successfully treated, others may cause a baby to be permanently disabled or even die. When diagnosed and treated early, almost all STDs can be successfully treated. People who have AIDS are very susceptible to many life-threatening diseases and to certain forms of cancer. Transmission of the virus occurs during sexual activity, as well as by the sharing of needles used to inject intravenous drugs.