More efficient allocation of HIV treatment may lead to disease containment and case reduction in South Africa, according to a study done by a pair of Yale researchers.

Elisa Long, an assistant professor at both the Yale School of Management and the Yale School of Public Health, and resident Robert Stavert MED ’09 SOM ’09 from the Yale School of Medicine have developed mathematical models that demonstrate the medical effectiveness and economic benefits of combining types of HIV treatments. Long and Stavert’s paper was published in the April issue of the Journal of General Internal Medicine.

“In the last five years, the landscape of HIV prevention has really changed dramatically, and in a setting like South Africa that has limited HIV resources, one question is how can we best allocate limited resources most effectively and cost-effectively in order to mitigate this huge epidemic,” Long said.

This scarcity of medical resources has forced researchers to find creative ways to redistribute funds and supplies efficiently to those that need them. To find the most cost-effective combination of treatments, Long investigated existing methods of preventing HIV, which include male circumcision, HIV screening and oral pre-exposure prophylaxis (PrEP), an ingestive medication.

When applied in isolation, the more common preventative measures like circumcision yield success rates of 30 to 60 percent, Long said. Certain other methods, such as the PrEP treatment, generally have higher success rates in isolation, but are also significantly more expensive and harder to distribute. As a result, Long and Stavert have proposed a “portfolio approach,” which uses a combination of cheaper, cost-effective treatment options instead of a single more expensive one.

“We have a number of programs that are currently within reach. On their own, they may not have a substantial impact on the epidemic. But in an aggregate manner, this portfolio of interventions could avert up to two-thirds of HIV cases over the next 10 years. We view this multi-faceted approach as our best chance of having a big impact on the epidemic while we wait for more advanced methods,” Long said.

One of the biggest obstacles in treating HIV has been dealing with the effects of secondary transmission — the spread of the disease from person to person, Long said. She contends, however, that this phenomenon can actually facilitate the containment of the disease.

“If we avert 30 percent of cases in men due to circumcision, we also prevent, let’s say, six percent of cases in women just through this modality of secondary transmission,” she added.

Currently, few clinical trials are being conducted to analyze the effectiveness of combining these intervention programs, forcing Long to generate her analysis through the use of mathematical models. What has been particularly innovative about her approach is her application of operations research techniques to addressing a public health issue, said Gregg Gonsalves, an HIV activist and visiting lecturer at the Yale Law School.

Gonsalves said he has been impressed with Long’s ability to analyze the HIV epidemic through this partly-mathematical, partly-economic lens.

“Coming from someone who has worked in HIV for a long time, [Long] is pioneering a whole area of thinking about operations research in the context of HIV. It’s really important to figure out how to do things most efficiently, cost-effectively and with the biggest bang for the buck,” he added.

Long estimates that over 5 million South Africans are currently infected with HIV.