Editors' ChoiceCommunity Medicine

The ART of Movers and Shakers

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Science Translational Medicine  27 Jun 2012:
Vol. 4, Issue 140, pp. 140ec112
DOI: 10.1126/scitranslmed.3004507

Antiretroviral therapy (ART) has extraordinary benefits; it both increases the life expectancy of HIV-infected individuals to almost that of their uninfected counterparts and decreases rates of HIV transmission from infected to susceptible individuals. Mathematical modeling studies have predicted that with high population coverage of testing and treatment (>90% of HIV-infected individuals), ART can dramatically decrease the number of new cases of HIV to close to zero. This prediction has stimulated the planning of several large studies in South Africa, Tanzania, and Botswana to examine the effectiveness of this test-and-treat strategy. Once identified, HIV-infected individuals must be linked to and retained in care, including ART. In an insightful mathematical modeling study, Andrews and colleagues illustrated that failing either to link HIV-infected individuals to care or to account for mobility of clients may undermine the population-level impact of planned large-scale HIV treatment trials on HIV prevention.

Andrews and colleagues used mathematical models to predict the long-term impact of current patterns of linkage to care and mobility on the prevention impact of HIV treatment programs in South Africa. They explicitly modeled individuals who repeatedly declined testing or treatment—and thus do not link to care—as well as those that moved in or out of study communities until these patients developed advanced, symptomatic disease. Using demographic, clinical, immigration, emigration, and linkage data from a South African township, Masiphumelele, the authors found that with explicit inclusion of observed linkage to care patterns, HIV elimination (new cases of <0.1% per year) did not occur over a 30-year time frame. Including mobility data further reduced the benefits of HIV treatment for prevention. Importantly, the model predictions were more sensitive to assumptions about the structural parameters of the model, such as linkage to care and population migration, than actual parameter values, which supports a broader application of this model outside of this patient population.

These realities of linkages to care and mobility are challenges that both research studies and health care programs can rise to. Businesses, such as banks and HMOs, provide services to clients on the go from Dar es Salem to Durban. The planned test and treat trials will use strategies with early promising success to increase linkages to care (all three studies plan to use home-based HIV counseling and testing) and identify new residents. In addition, innovative communication tools could be used to motivate clients and facilitate linkage care. Demonstrating the impact of these strategies is necessary to ensure that the full benefits of ART for prevention are realized.

J. R. Andrews et al., Projecting the benefits of antiretroviral therapy for HIV prevention: The impact of population mobility and linkage to care. J. Infect. Dis. 18 June 2012 (10.1093/infdis/jis401). [Abstract]

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