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Abstract
Population effects of different individual risk factors and control efforts
J S Koopman, C P Simon
U of Mich, Ann Arbor, United States
Background HIV transmission models demonstrate that most of the population effects of risk factors are indirect, due to transmission dynamics, rather than from causal actions directly on individuals with the risk factors. Thus, a general framework for predicting indirect effects is needed to set infection control priorities. Methods An SI model was analyzed. The population was divided into a low-risk and a high-risk group (HRG). Contact patterns examined covered the full range possible. The increased risk in the HRG was generated by either increased susceptibility (S), infectiousness (I), infection duration (D), or contact rates (CR). In each of these situations, S, I, D or CR were reduced in the HRG by 5% or in the general population by an equivalent amount. Results Across all 4 causes of high risk, interventions on individual risk factors had greater population effects than would be predicted by standard individual counter-factual risk assessment methods. Effects of interventions were dramatically greater when concentrated on the HRG. All population effects were highly dependent upon contact patterns. Iinterventions focused on the HRG always had their smallest effects at completely assortative mixing. In contrast, interventions in the general population generally had their greatest effects there. S effects were generally smaller than the other effects. I and D had comparable effects at equilibrium but different dynamics. CR effects were generally greater than all other intervention effects but varied with assumptions about how the interventions affected mixing patterns. Conclusions Standard epidemiological studies that compare infection incidence in individuals with and without a risk factor distort our focus on the most productive risk factors to control. Studies that link HIV nucleotide sequences to epidemiological data might capture the theoretical population effects of risk factors and contact patterns demonstrated here.
The XIV International AIDS Conference
Abstract no.
C10917
Suggested Citation
" J S Koopman, et al.
Population effects of different individual risk factors and control efforts
.
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The XIV International AIDS Conference:
Abstract no.
C10917"
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