South African Center for Epidemiological Modelling and Analysis

Stellenbosch, South Africa

South African Center for Epidemiological Modelling and Analysis

Stellenbosch, South Africa
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Williams B.G.,South African Center for Epidemiological Modelling and Analysis | Lima V.,St Pauls Hospital | Gouws E.,Joint United Nations Programme on HIV AIDS UNAIDS
Current HIV Research | Year: 2011

Thirty years after HIV first appeared it has killed close to 30 million people but transmission continues unchecked. In 2009, an estimated 1.8 million lives were lost and 2.6 million more people were infected with HIV [1]. To cut transmission, many social, behavioural and biomedical interventions have been developed, tested and tried but have had little impact on the epidemic in most countries. One substantial success has been the development of combination antiretroviral therapy (ART) that reduces viral load and restores immune function. This raises the possibility of using ART not only to treat people but also to prevent new HIV infections. Here we consider the impact of ART on the transmission of HIV and show how it could help to control the epidemic. Much needs to be known and understood concerning the impact of early treatment with ART on the prognosis for individual patients and on transmission. We review the current literature on factors associated with modelling treatment for prevention and illustrate the potential impact using existing models. We focus on generalized epidemics in subSaharan Africa, with an emphasis on South Africa, where transmission is mainly heterosexual and which account for an estimated 17% of all people living with HIV. We also make reference to epidemics among men who have sex with men and injection drug users where appropriate. We discuss ways in which using treatment as prevention can be taken forward knowing that this can only be the beginning of what must become an inclusive dialogue among all of those concerned to stop acquired immune deficiency syndrome (AIDS). © 2011 Bentham Science Publishers.


Dye C.,World Health Organization | Trunz B.B.,Petit Lancy | Lonnroth K.,World Health Organization | Roglic G.,World Health Organization | Williams B.G.,South African Center for Epidemiological Modelling and Analysis
PLoS ONE | Year: 2011

Background: Diabetes prevalence and body mass index reflect the nutritional profile of populations but have opposing effects on tuberculosis risk. Interactions between diabetes and BMI could help or hinder TB control in growing, aging, urbanizing populations. Methods and Findings: We compiled data describing temporal changes in BMI, diabetes prevalence and population age structure in rural and urban areas for men and women in countries with high (India) and low (Rep. Korea) TB burdens. Using published data on the risks of TB associated with these factors, we calculated expected changes in TB incidence between 1998 and 2008. In India, TB incidence cases would have increased (28% from 1.7 m to 2.1 m) faster than population size (22%) because of adverse effects of aging, urbanization, changing BMI and rising diabetes prevalence, generating an increase in TB incidence per capita of 5.5% in 10 years. In India, general nutritional improvements were offset by a fall in BMI among the majority of men who live in rural areas. The growing prevalence of diabetes in India increased the annual number of TB cases in people with diabetes by 46% between 1998 and 2008. In Korea, by contrast, the number of TB cases increased more slowly (6.1% from 40,200 to 42,800) than population size (14%) because of positive effects of urbanization, increasing BMI and falling diabetes prevalence. Consequently, TB incidence per capita fell by 7.8% in 10 years. Rapid population aging was the most significant adverse effect in Korea. Conclusions: Nutritional and demographic changes had stronger adverse effects on TB in high-incidence India than in lower-incidence Korea. The unfavourable effects in both countries can be overcome by early drug treatment but, if left unchecked, could lead to an accelerating rise in TB incidence. The prevention and management of risk factors for TB would reinforce TB control by chemotherapy. © 2011 Dye et al.


Kato M.,World Health Organization | Granich R.,World Health Organization | Bui D.D.,Ministry of Health | Tran H.V.,Partners in Health Research | And 7 more authors.
Journal of Acquired Immune Deficiency Syndromes | Year: 2013

Background: Few studies have assessed the effects of antiretroviral therapy (ART) to prevent HIV transmission in Asian HIV epidemics. Vietnam has a concentrated HIV epidemic with the highest prevalence among people who inject drugs. We investigated the impact of expanded HIV testing and counseling (HTC) and early ART, combined with other prevention interventions on HIV transmission. Methods: A deterministic mathematical model was developed using HIV prevalence trends in Can Tho province, Vietnam. Scenarios included offering periodic HTC and immediate ART with and without targeting subpopulations and examining combined strategies with methadone maintenance therapy and condom use. Results: From 2011 to 2050, maintaining current interventions will incur an estimated 18,115 new HIV infections and will cost US $22.1 million (reference scenario). Annual HTC and immediate treatment, if offered to all adults, will reduce new HIV infections by 14,513 (80%) and will cost US $76.9 million. Annual HTC and immediate treatment offered only to people who inject drugs will reduce new infections by 13,578 (75%) and will cost only US $23.6 million. Annual HTC and immediate treatment for key populations, combined with scale-up of methadone maintenance therapy and condom use, will reduce new infections by 14,723 (81%) with similar costs (US $22.7 million). This combination prevention scenario will reduce the incidence to less than 1 per 100,000 in 14 years and will result in a relative cost saving after 19 years. Conclusions: Targeted periodic HTC and immediate ART combined with other interventions is cost-effective and could lead to potential elimination of HIV in Can Tho. Copyright © 2013 by Lippincott Williams & Wilkins.


Harries A.D.,International Union Against Tuberculosis and Lung Disease | Harries A.D.,London School of Hygiene and Tropical Medicine | Zachariah R.,Médecins Sans Frontières | Corbett E.L.,London School of Hygiene and Tropical Medicine | And 10 more authors.
The Lancet | Year: 2010

Despite policies, strategies, and guidelines, the epidemic of HIV-associated tuberculosis continues to rage, particularly in southern Africa. We focus our attention on the regions with the greatest burden of disease, especially sub-Saharan Africa, and concentrate on prevention of tuberculosis in people with HIV infection, a challenge that has been greatly neglected. We argue for a much more aggressive approach to early diagnosis and treatment of HIV infection in affected communities, and propose urgent assessment of frequent testing for HIV and early start of antiretroviral treatment (ART). This approach should result in short-term and long-term declines in tuberculosis incidence through individual immune reconstitution and reduced HIV transmission. Implementation of the 3Is policy (intensified tuberculosis case finding, infection control, and isoniazid preventive therapy) for prevention of HIV-associated tuberculosis, combined with earlier start of ART, will reduce the burden of tuberculosis in people with HIV infection and provide a safe clinical environment for delivery of ART. Some progress is being made in provision of HIV care to HIV-infected patients with tuberculosis, but too few receive co-trimoxazole prophylaxis and ART. We make practical recommendations about how to improve this situation. Early HIV diagnosis and treatment, the 3Is, and a comprehensive package of HIV care, in association with directly observed therapy, short-course (DOTS) for tuberculosis, form the basis of prevention and control of HIV-associated tuberculosis. This call to action recommends that both HIV and tuberculosis programmes exhort implementation of strategies that are known to be effective, and test innovative strategies that could work. The continuing HIV-associated tuberculosis epidemic needs bold but responsible action, without which the future will simply mirror the past. © 2010 Elsevier Ltd. All rights reserved.


Granich R.,UNAIDS | Williams B.,South African Center for Epidemiological Modelling and Analysis | Montaner J.,British Columbia Center for Excellence in
Current Opinion in HIV and AIDS | Year: 2013

PURPOSE OF REVIEW: The declaration of the United Nations High Level meeting on AIDS in June 2011 includes 10 concrete targets, including to ensure that there are 15 million people living with human immunodeficiency virus (HIV) on antiretroviral treatment (ART) by 2015. This review examines the potential, opportunities and challenges of treatment as prevention of HIV and tuberculosis (TB) in reaching this target. RECENT FINDINGS: Although around 8 million people are on treatment, everyone living with HIV will eventually need ART to stay alive. As many as 24million people living with HIV today are not on treatment, the majority not even being aware of their HIV infection. Expansion of a comprehensive prevention strategy including providing ART to 15 million or more people would significantly reduce HIV and TB morbidity, mortality and transmission. The challenges include ensuring human rights protections, steady drug supply, early diagnosis and linkage to care, task shifting, adherence, retention, and monitoring and evaluation. Expansion could also lead to the control and possible elimination of HIV in many places. SUMMARY: Achieving an 'AIDS-free generation' whereby deaths related to HIV are drastically reduced, people living with HIV are AIDS-free on ART, and HIV transmission is decreased, is both scientifically sound and practically feasible. The global community could reach 15 million people on ART by 2015 while expanding our vision and efforts to include diagnosis and treatment for all the 32million people living with HIV in the future. © Lippincott Williams & Wilkins.


Tiemersma E.W.,KNCV Tuberculosis Foundation | Tiemersma E.W.,University of Amsterdam | van der Werf M.J.,KNCV Tuberculosis Foundation | van der Werf M.J.,University of Amsterdam | And 3 more authors.
PLoS ONE | Year: 2011

Background: The prognosis, specifically the case fatality and duration, of untreated tuberculosis is important as many patients are not correctly diagnosed and therefore receive inadequate or no treatment. Furthermore, duration and case fatality of tuberculosis are key parameters in interpreting epidemiological data. Methodology and Principal Findings: To estimate the duration and case fatality of untreated pulmonary tuberculosis in HIV negative patients we reviewed studies from the pre-chemotherapy era. Untreated smear-positive tuberculosis among HIV negative individuals has a 10-year case fatality variously reported between 53% and 86%, with a weighted mean of 70%. Ten-year case fatality of culture-positive smear-negative tuberculosis was nowhere reported directly but can be indirectly estimated to be approximately 20%. The duration of tuberculosis from onset to cure or death is approximately 3 years and appears to be similar for smear-positive and smear-negative tuberculosis. Conclusions: Current models of untreated tuberculosis that assume a total duration of 2 years until self-cure or death underestimate the duration of disease by about one year, but their case fatality estimates of 70% for smear-positive and 20% for culture-positive smear-negative tuberculosis appear to be satisfactory. © 2011 Tiemersma et al.


Williams B.G.,South African Center for Epidemiological Modelling and Analysis | Abdool Karim S.S.,Columbia University | Karim Q.A.,Columbia University | Gouws E.,UNAIDS Joint United Nations Program on HIV AIDS
Journal of Acquired Immune Deficiency Syndromes | Year: 2011

Background: Tenofovir gel, an antiretroviral-based vaginal microbicide, reduced HIV acquisition by 39% in women in a recent randomized controlled clinical trial in South Africa. Methods: To inform policy, we used a dynamical model of HIV transmission, calibrated to the epidemic in South Africa, to determine the population-level impact of this microbicide on HIV incidence, prevalence, and deaths and to evaluate its cost-effectiveness. Results: If women use tenofovir gel in 80% or more of sexual encounters (high coverage), it could avert 2.33 (0.12 to 4.63) million new infections and save 1.30 (0.07 to 2.42) million lives and if used in 25% of sexual encounters (low coverage), it could avert 0.50 (0.04 to 0.77) million new infections and save 0.29 (0.02 to 0.44) million deaths, over the next 20 years. At US $0.50 per application, the cost per infection averted at low coverage is US $2392 (US $562 to US $4222) and the cost per disability-adjusted life year saved is US $104 (US $27 to US $181); at high coverage the costs are about 30% less. Conclusions: Over 20 years, the use of tenofovir gel in South Africa could avert up to 2 million new infections and 1 million AIDS deaths. Even with low rates of gel use, it is highly cost-effective and compares favorably with other control methods. This female-controlled prevention method could have a significant impact on the epidemic of HIV in South Africa. Programs should aim to achieve gel use in more than 25% of sexual encounters to significantly alter the course of the epidemic. © 2011 by Lippincott Williams & Wilkins.


Gupta S.,Independent Consultant | Williams B.,South African Center for Epidemiological Modelling and Analysis | Montaner J.,Center for Excellence in AIDS
Current HIV/AIDS Reports | Year: 2014

This article reviews the antiretroviral therapy (ART) initiation criteria from published national guidelines for 94 countries (representing 86 % of global HIV burden) and compares them with the 2013 World Health Organization (WHO) ART guidelines. As of 31st of July 2014, 19 countries have adopted the WHO-recommended CD4 eligibility criteria of ≤500 cells/mm3, while seven have opted to treat irrespective of CD4 cell count (“test and treat”). Together, these 26 countries represent 27 % of 2013 global HIV burden. Additionally, test and treat is recommended for selected groups of HIV-positive individuals, namely, (a) people with tuberculosis in 58 countries, (b) pregnant women in 42 countries, (c) people with liver disease due to hepatitis B co-infection in 52 countries, (d) serodiscordant couples in 35 countries and (e) children below 5 years in nine countries. Global access to treatment has improved; however in 2013, ART coverage was 12.9 million or 37 % of people living with HIV. Rapidly translating new science into policy is a critical component of the HIV response. Adapting and implementing the 2013 WHO treatment recommendations are necessary to prevent unnecessary illness, death, HIV transmission and costs. © 2014, Springer Science+Business Media New York.


Cohen M.S.,University of North Carolina at Chapel Hill | Dye C.,World Health Organization | Fraser C.,Imperial College London | Miller W.C.,University of North Carolina at Chapel Hill | And 2 more authors.
PLoS Medicine | Year: 2012

Universal HIV testing and immediate antiretroviral therapy for infected individuals has been proposed as a way of reducing the transmission of HIV and thereby bringing the HIV epidemic under control. It is unclear whether transmission during early HIV infection-before individuals are likely to have been diagnosed with HIV and started on antiretroviral therapy-will compromise the effectiveness of treatment as prevention. This article presents two opposing viewpoints by Powers, Miller, and Cohen, and Williams and Dye, followed by a commentary by Fraser. © 2012 Cohen et al.


Dye C.,World Health Organization | Williams B.G.,South African Center for Epidemiological Modelling and Analysis
Science | Year: 2010

More than 36 million patients have been successfully treated via the World Health Organization's strategy for tuberculosis (TB) control since 1995. Despite predictions of a decline in global incidence, the number of new cases continues to grow, approaching 10 million in 2010. Here we review the changing relationship between the causative agent, Mycobacterium tuberculosis, and its human host and examine a range of factors that could explain the persistence of TB. Although there are ways to reduce susceptibility to infection and disease, and a high-efficacy vaccine would boost TB prevention, early diagnosis and drug treatment to interrupt transmission remain the top priorities for control. Whatever the technology used, success depends critically on the social, institutional, and epidemiological context in which it is applied.

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