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September 29, 1999

Treating Sexually Transmitted Diseases Does Not Reduce HIV Incidence in Mature HIV Epidemics

Strategies for treating sexually transmitted diseases (STDs) are unlikely to substantially reduce the incidence of HIV in mature, generalized, HIV epidemic settings, according to a recent study by researchers at the Johns Hopkins School of Public Health. The study, which appeared in the October issue of AIDS, found that most HIV infection occurs without recognized STD symptoms or treatable STD diagnosis.

Lead author Ronald Gray, MD, MSc, professor, Population and Family Health Sciences, Johns Hopkins School of Public Health, said, "The findings suggest that STD infections and genital tract lesions may be causal co-factors for contracting and transmitting HIV at an individual level, but in a mature epidemic, with high background rates of HIV, it is unlikely that treatment of STDs can be used as a public health measure to reduce HIV incidence in populations."

The study monitored consenting East African adults between the ages of 15-59 during five home visits at 10-month intervals. At each contact the subjects were interviewed regarding STD symptoms and asked to provide samples for HIV and STD testing. Within the original study group, a sub-group of HIV "discordant" couples, that is couples where one partner is HIV-positive and the other is HIV-negative, was also examined.

The results of the study showed that HIV prevalence was 16 percent. The risk for acquiring HIV because of genital ulcers was increased in both men and women and the risk of HIV infections was increased in men with discharge symptoms but not in women with discharge. The population attributable fraction (PAF) was used to measure the proportion of new HIV infections that were attributable to STDs. The PAF of HIV acquisition was 9.5 percent with any of three STD symptoms. The PAF for genital ulcer disease (GUD) was 8.8 percent; however, only 8.2 percent of GUDs were caused by curable syphilis or chancroid, and most ulcers were due to herpes infection, which could not be cured in this setting. The PAF of HIV transmission associated with STD symptoms in HIV-positive persons within discordant relationships was indirectly estimated to be 10.4 percent. Thus, in the best case scenario, even if all symptomatic persons could be treated and if all symptoms were due to curable STDs, HIV incidence could only be reduced by about 20 percent in this epidemic setting.

The study results suggest that in a generalized HIV epidemic setting, HIV infection occurs independently of other curable STDs. Therefore, managing and treating STDs may not help to substantially reduce HIV incidence in the general population. However, the fact remains that STDs are associated with significant HIV risk at the individual level and should continue to be treated in order to protect such individuals.

The study was supported by grants from the National Institute of Allergy and Infectious Diseases, the National Institute of Child Health and Development, the Rockefeller Foundations and the World Bank Uganda STI Project.

Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham @ 410-955-6878 or paffairs@jhsph.edu.