In 2015, Scott County, Indiana, experienced the largest HIV outbreak among people who inject drugs in a nonurban setting in the United States, with more than 180 cases in a community of about 24,000. Reacting to the outbreak, the state health officials implemented a syringe services program, but researchers now say that proactive implementation of the program had the potential to avert 90.3% of infections.
“There are an estimated 3 million people who inject drugs (PWID) living with HIV worldwide. While there have been great successes in reducing HIV transmission in some settings, there have been outbreaks in recent years,” William C. Goedel, of the department of epidemiology at Brown University’s School of Public Health, and colleagues wrote. “Several factors have been associated with rapid HIV transmission among PWID, including limited access to sterile injection equipment and other harm-reduction services, including syringe services programs. However, predicting where these outbreaks may occur is difficult.”
To test the effects of proactively implementing a syringe services program, researchers used an agent-based model simulating HIV transmission in Scott County, where the prevalence of injection drug use is 1.7%. Researchers compared the outcomes of three scenarios — the absence of a syringe services program, the presence of a pre-existing program and the implementation of a program after the detection of an HIV outbreak.
Results showed that in the absence of a syringe services program, the model predicted an average of 176 infections among PWID over 5 years. They learned that proactive implementation averted 154 infections and decreased incidence by 90.3%, and that reactive implementation beginning operations 10 months after the first infection would prevent 107 infections and decrease incidence by 60.8%. Additionally, researchers found that reductions in incidence were also observed among people who did not inject drugs with proactive implementation.
“Based on model predictions, proactive implementation of [a syringe services program] in Scott County had the potential to avert more HIV infections than reactive implementation after the detection of an outbreak. The predicted impact of reactive [syringe services program] implementation was highly dependent on the timely detection of the earliest infections,” the authors concluded. “Consequently, there is a need for expanded proactive [syringe services program] implementation in the context of enhanced monitoring of outbreak vulnerability in Scott County and in similar rural contexts.”
Findings from another modelling study, published in The Lancet HIV, showed that a swifter public health response could have prevented or drastically mitigated the Scott County outbreak. Then-Indiana Gov. Mike Pence declared a public health emergency 2 months after the outbreak had peaked. Findings from the study showed that if a public health intervention began in 2011, the cumulative HIV incidence would have been reduced to 10 or fewer cases. – by Caitlyn Stulpin
Goedel WC, et al. Clin Infect Dis. 2019;doi:10.1093/cid/ciz321.
Gonsalves GS, Crawford FW. Lancet HIV. 2018;doi:10.1016/S2352-3018(18)30176-0.
Disclosures: The authors report no relevant financial disclosures.