AEGiS-14IAC: Strategies for reducing the burden of TB infection and disease in high HIV prevalence populations: modelling the impact of active case finding, antiretrovirals and preventive therapy.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Strategies for reducing the burden of TB infection and disease in high HIV prevalence populations: modelling the impact of active case finding, antiretrovirals and preventive therapy.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. WeOrC1312)

Corbett EL, Currie C, Churchyard GJ, Williams BG
London School of Hygiene and Tropical Medicine, London, United Kingdom

BACKGROUND: The HIV epidemic has greatly worsened TB control in Africa. Gold miners are a closely studied population in whom new control strategies are being considered.

METHODS: We adapted existing mathematical models of TB, and simulated an HIV epidemic to fit data on time trends of TB incidence and prevalence in HIV+ve and HIV-ve gold miners, in order to investigate different approaches to improving TB control.

RESULTS: Several strategies led to major (>70%) reductions in projected TB incidence, but rapidity of onset and durability varied. The most successful in the short-term was a single round of mass case-finding plus mass preventive therapy (PT), which simultaneously reduced the burden of latent TB infection, prevalent TB disease and TB transmission. Durability, however, was < 10yrs unless combined with ongoing measures. Without an initial round of mass PT, antiretroviral therapy (ART), PT targeted to HIV+ve miners (targeted PT), and increased active case-finding had slow onset, and were limited by uptake of HIV-testing. A potentially paradoxical effect of widespread ART was observed. If the net effect was to increase absolute numbers in the mid or late stages of immunosuppression, for example by intermittent therapy aimed at symptomatic individuals, then overall TB incidence increased along with workforce HIV prevalence. If, however, normal immune function was maintained, then TB incidence decreased despite increasing HIV prevalence.

CONCLUSIONS: New strategies capable of controlling TB in high HIV prevalence areas are urgently needed. Our model suggests that combined approaches that tackle both latent TB and ongoing TB transmission are likely to be most successful, particularly when not exclusively targeted to those of known HIV status. Care is needed when introducing ART into high HIV prevalence populations, as some strategies may have a deleterious impact on the control of HIV-associated infections, such as TB.

Keywords: AEGIS, Prevalence, HIV Infections, Incidence, HIV Seropositivity, Mining, Disease Outbreaks, Gold, Africa, prevention & control, epidemiology

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