The Link Between HIV and Other STDs

November 1996

The link between HIV infection and other sexually transmitted diseases (STDs) has now been clearly established. The Centers for Disease Control and Prevention (CDC) is applying new research to prevent all of the major STDs, including HIV infection, and to ensure that communities have the information they need to design, implement, and evaluate comprehensive approaches to HIV/STD prevention programming.

Evidence of the Link: Parallel Epidemics of HIV Infection and Other STDs

The spread of HIV infection in the United States through sexual transmission has followed in the footsteps of other STD epidemics. For example, the geographic distribution of the emerging problem of heterosexual HIV transmission in the South closely parallels that of syphilis. Most of the health districts with the highest syphilis and gonorrhea rates in the U.S. are concentrated in the southern part of the country, the same part of the nation where HIV prevalence among childbearing women also is highest.

In addition, researchers have long recognized that the behaviors which place individuals at risk for other STDs also increase their risk of becoming infected with HIV. STD surveillance can provide important indications of where HIV infection may spread, and where efforts to promote safer sexual behaviors should be targeted.

Other STDs Facilitate HIV Transmission: Biological Basis for the Link

There is now strong population-based and biological evidence that the presence of other STDS increases the likelihood of both transmitting and acquiring HIV. Conversely, increased STD treatment can slow the spread of HIV.

  • Epidemiological studies: Prospective epidemiological studies have repeatedly demonstrated in groups over time, that when other STDs are present, HIV transmission is at least twofold to fivefold higher than in groups where other STDs are not present.

  • Biological studies: Biological studies demonstrate that when other STDs are present, the susceptibility to HIV infection is increased and the likelihood of infecting other people is increased.

    a)Increased susceptibility -- Other STDs increase the number of HIV target cells (CD4+ cells) in cervical secretions, thereby probably increasing HIV susceptibility in women who have an HIV-positive sex partner.

    b) Increased infectiousness -- Studies have demonstrated that when HIV-infected individuals are also infected with other STDs, they are more likely to shed HIV in genital secretions, and shed HIV in greater amounts. For example, in African studies, coinfection with gonorrhea and HIV more than doubles the proportion of HIV-infected individuals with HIV genetic material detectable in genital secretions compared with men infected with HIV alone. Furthermore, the median concentration of HIV genetic material in semen is dramatically increased in coinfected men compared with men infected with HIV alone.

    New Evidence that STD Treatment Slows the Spread of HIV Infection in Communities

  • Intervention studies: Exciting new evidence indicates that STD detection and treatment can substantially reduce HIV transmission at the individual and community levels. For example:

    a)STD treatment reduces the frequency and magnitude of HIV shedding-- Treatment of gonorrhea in HIV-infected men returns the concentration of HIV genetic material in semen to baseline levels. These levels are comparable to the levels found in HIV-infected men who do not have other STDs. Treatment of gonorrhea also reduced the proportion of the coinfected men who had detectable levels of HIV genetic material in semen.

    b)STD treatment reduces the spread of HIV infection in communities -- A landmark community-level, randomized trial in a rural African community in Tanzania demonstrated a 42% decrease in new, heterosexually transmitted HIV infections in communities with improved STD treatment as compared to communities with minimal STD services. An ongoing randomized trial in Uganda is exploring alternative approaches, such as mass treatment for STDs, to further examine the impact of STD control on HIV prevention. The results of these studies will be crucial to validating the findings of the Tanzanian trial and to providing a range of intervention models for reducing the spread of HIV infection in communities with high rates of other STDs, both in the developing world and in industrialized countries.

    STD Prevention, Detection, and Treatment are Essential Components of HIV Prevention

    Detection and treatment of other STDs reduce both the infectiousness of persons with HIV infection and the susceptibility of persons who are not HIV-infected. Detection and treatment of other STDs are essential components of HIV prevention.

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