growth and rural-to-urban migration, that contribute to the spread of STDs in both developed and developing countries. The advent of new techniques in biotechnology have allowed the presence of infectious organisms or genetic material from these organisms to be detected, contributing to the recognition of new sexually transmitted infections. These techniques have allowed clinicians and epidemiologists to link specific infectious organisms to the syndromes that they cause.
STDs are severe social, health, and economic burdens worldwide. STDs most commonly affect people who are between the ages of 15 and 44, the group that is most economically productive (Over and Piot, 1993). The World Bank estimates that STDs, excluding AIDS, are the second leading cause of healthy life lost among women between the ages of 15 and 44 in the developing world (Figure 2-3) (World Bank, 1993). STDs are severe public health problems because of their potentially serious complications as well as their potential to increase the efficiency of HIV transmission. One study estimated that the impact of successfully treating or preventing one hundred cases of syphilis among a group at high risk for STDs would prevent 1,200 HIV infections that would otherwise be linked to those one hundred syphilis infections during a 10-year period (Over and Piot, 1993). Over and Piot (1996) also found that, in developing countries, targeting groups with the highest rates of sex partner change markedly improves the cost-effectiveness of HIV and other STD prevention efforts.
The World Health Organization (WHO) Global Programme on AIDS recently estimated regional and global incidence rates for four curable STDs-gonorrhea, chlamydial infection, syphilis, and trichomoniasis (WHO, 1996). Using a database of country-specific prevalence rates and estimated regional prevalence rates for each curable STD, WHO estimated that there were 333 million new cases of the four curable STDs worldwide in 1995 among adults 15-49 years of age. Prevalence rates for other STDs for which estimates are not available, such as human papillomavirus and herpes simplex virus type 2 infections, are much higher, and the number of adults infected is likely to exceed one billion. In addition, in the last few years, STDs have rapidly become epidemic in some areas of the world, such as certain countries of the former Soviet Union. These epidemics have relevance for the United States because Americans are increasingly traveling abroad, and some will have high-risk sexual intercourse during their stay (Moore et al., 1995). With increasing access to international travel and easing of travel restrictions, it is now possible for persons with infectious diseases to spread their infection to others around the world in a matter of hours or days.