Syphilis, HIV, hepatitis B and C are all serious illnesses that can cause long-term health problems and even death. Teens and young adults are particularly vulnerable to these diseases, as they are more likely to have multiple sexual partners and may not be aware of how to protect themselves. Drug users who use contaminated needles are also at risk. STDs are serious medical conditions that require treatment.
Some, such as HIV, cannot be cured and can be fatal if left untreated. Studies of couples in which one partner was HIV-positive and the other was not have shown that other STDs do not increase the risk of HIV transmission. Several studies have demonstrated that early detection and treatment of STDs can have a significant impact on reducing the spread of HIV through sexual contact. These models are complex and depend on many assumptions related to sexual behavior, the natural history and epidemiology of STDs, and interactions between STDs and HIV.
In the absence of prospective studies or formal trials of reinforced interventions against STDs to reduce sexual transmission of HIV in the United States (which may not be feasible), mathematical models may be essential to assess the potential impact of reducing STDs on HIV transmission. Women are more likely to suffer from STDs than men, as they are more susceptible to infection, more likely to have undetected infections, and more likely to experience complications from STDs. Results from important epidemiological studies have shown that people with certain existing sexually transmitted diseases are at an increased risk for subsequent HIV infection. Other sexually transmitted diseases of particular concern for men who have sex with men include anal syphilis, urethritis, and a variety of oral and gastrointestinal infections.
However, serosurvey data indicate that the differences in STD rates between racial and ethnic groups are actually smaller than those suggested by national surveillance data. Estimating the impact of preventive interventions on the transmission of STDs in a population is extremely complex. The term STD is not specific to any one disease, but rather encompasses more than 25 infectious organisms that can be transmitted through sexual activity and the dozens of clinical syndromes they cause (Appendix A). Thanks to advances in modern science, mortality rates from sexually transmitted diseases are generally lower now than in the past.
As emerging and re-emerging infections, new sexually transmitted infections appear regularly and are likely to continue to do so as long as rates of risky sexual behavior remain high and global economic and demographic factors continue to promote the emergence of new STDs. However, the strongest evidence on the relationship between STDs and HIV transmission in the United States relates to heterosexual transmission of HIV. Over the past two decades, adolescent sexual relationships have increased steadily, resulting in an increasing number of young men and women at risk of contracting sexually transmitted diseases (CDC, 1995c). Several approaches have been used to model the impact of several determinants on the spread of HIV and other STDs and the influence of other STDs on the HIV epidemic (Appendix C).