23 research outputs found
Assessment of epidemic projections using recent HIV survey data in South Africa: A validation analysis of ten mathematical models of HIV epidemiology in the antiretroviral therapy era
Background: Mathematical models are widely used to simulate the effects of interventions to control HIV and to project future epidemiological trends and resource needs. We aimed to validate past model projections against data from a large household survey done in South Africa in 2012. Methods: We compared ten model projections of HIV prevalence, HIV incidence, and antiretroviral therapy (ART) coverage for South Africa with estimates from national household survey data from 2012. Model projections for 2012 were made before the publication of the 2012 household survey. We compared adult (age 15-49 years) HIV prevalence in 2012, the change in prevalence between 2008 and 2012, and prevalence, incidence, and ART coverage by sex and by age groups between model projections and the 2012 household survey. Findings: All models projected lower prevalence estimates for 2012 than the survey estimate (18路8%), with eight models' central projections being below the survey 95% CI (17路5-20路3). Eight models projected that HIV prevalence would remain unchanged (n=5) or decline (n=3) between 2008 and 2012, whereas prevalence estimates from the household surveys increased from 16路9% in 2008 to 18路8% in 2012 (difference 1路9, 95% CI -0路1 to 3路9). Model projections accurately predicted the 1路6 percentage point prevalence decline (95% CI -0路3 to 3路5) in young adults aged 15-24 years, and the 2路2 percentage point (0路5 to 3路9) increase in those aged 50 years and older. Models accurately represented the number of adults on ART in 2012; six of ten models were within the survey 95% CI of 1路54-2路12 million. However, the differential ART coverage between women and men was not fully captured; all model projections of the sex ratio of women to men on ART were lower than the survey estimate of 2路22 (95% CI 1路73-2路71). Interpretation: Projections for overall declines in HIV epidemics during the ART era might have been optimistic. Future treatment and HIV prevention needs might be greater than previously forecasted. Additional data about service provision for HIV care could help inform more accurate projections. Funding: Bill & Melinda Gates Foundation
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Setting the tone - biomedical advances
Paper presented at the Reflections on IAC 2008, Cape Town, 29 Septembe
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From theory to practice: HIV incidence testing, South Africa 2012
Paper presented at the HIV Incidence Assay Symposium, CROI, Seattle, 23 Februar
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Second generation HIV surveillance
Paper presented at the M&E Workshop for AIDS Programme Managers, Cape Town, 10-11 Januar
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Practical application of HIV incidence testing: South Africa 2005 and 2008
Paper presented at the WHO HIV Incidence Assay Working Group, Mexico City, 2-3 Augus
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HIV/AIDS impact assessment study project: first trimester report March - July 2006
Prepared for Safety and Security Sector Education and Training Authority (SASSETA), AugustIn October 2005 SASSETA put out a tender to undertake a critical assessment of HIV/AIDS in the Private Security and Legal Services industries, in terms of the prevalence rate of HIV, business impact, and the responses of businesses to the epidemic thus far. Furthermore, the study seeks to establish both sufficient and reliable empirical data about the current status quo, which will then be the basis for forecasting the possible impact of HIV/AIDS on selected indicators within the sub-sectors.The tender was won by the HSRC and contract was signed on 7th March 2007. The duration of the project was earmarked for 12 months.
In order to gather such detailed information, the study will include an HIV sero-prevalence survey in the two sub-sectors, which will establish the nature and size of the impact, but also elucidate the risk or protective environment of the workforces in these sub-sectors. Such information will be fed into a demographic modelling tool, in order to establish the possible progress of the disease over time.
Finally, in order to establish baseline information on both the business impact of and business response to the disease, a stratified sample survey of employers and employees in the two sub-sectors will be conducted.
Such an objective evaluation will enable the SASSETA to make an informed decision, from a training perspective, on measures to facilitate effective HIV/AIDS intervention in the sub-sectors, via members and stakeholders
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Estimates of eligibility for antiretroviral treatment (ART) and projected ART impact on AIDS mortality among South African educators
This study assessed the proportion of HIV-infected educators that need antiretroviral treatment (ART) according to the current criteria and estimated the impact of ART on AIDS mortality by modelling scenarios with and without access to ART. Specimens for HIV testing were obtained from educators and a sub-sample of venous blood specimens from HIV-positive educators was selected for analysis.
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Epidemiological and demographic HIV/AIDS projections: South Africa
The Epidemic Projection Package (EPP) recently developed by the UNAIDS Reference Group on Estimates, Models and Projections and the Spectrum model program developed by the Futures Group were used to model the South African HIV epidemic, project future trends in HIV/AIDS and estimate the demographic impact of AIDS. The national HIV prevalence surveys among pregnant women from 1990-2001 and the first national, population-based HIV survey in 2002 served as the data sets used to calibrate the input HIV prevalence values for the model. The scenario created by the model showed that a dramatic rise in HIV prevalence during the 1990s has peaked in 2002 with 4.69 million infected people and it is projected that the epidemic in South Africa has now begun to level off. Adult (15-49 years) incidence rates have decreased substantially in the past five years since 1997 (4.2%) and are expected to reach a level of 1.7% in 2003. The annual number of deaths due to AIDS is projected to peak with 487 320 AIDS deaths in the year 2008. By 2020, the total population of South Africa is expected to be 23% smaller than it would be without AIDS, however, a negative population growth rate is not expected during the projection period. Life expectancy at birth is expected to hit a low of 45.6 years in the time period 2005-2010, which is 22 years less than it would have been in the absence of AIDS. Ten years from now over 2.5 million AIDS orphans are projected for South Africa. Models play an important role in estimating HIV variables that are difficult to measure. Projections of the future HIV/AIDS burden in South Africa underscore the importance of acting now to reduce the number of new infections and plan for medical and social care needs.
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The effect of changes in condom usage and antiretroviral treatment coverage on human immunodeficiency virus incidence in South Africa: a model-based analysis
This study aims to assess trends in human immunodeficiency virus (HIV) incidence in South Africa, and to assess the extent to which prevention and treatment programmes have reduced HIV incidence. Two models of the South African HIV epidemic, the STI (sexually transmitted infection) HIV Interaction model and the ASSA2003 AIDS and Demographic model, were adapted. Both models were fitted to age-specific HIV prevalence data from antenatal clinic surveys and household surveys, using a Bayesian approach. Both models suggest that HIV incidence in 15-49 year olds declined significantly between the start of 2000 and the
start of 2008: by 27 per cent (95% CI: 21-32%) in the STI/HIV model and by 31 per cent (95% CI: 23-39%) in the ASSA2003 model, when expressed as a percentage of incidence rates in 2000. By 2008, the percentage reduction in incidence owing to increased condom use was 37 per cent (95% CI: 34-41%) in the STI-HIV model and 23 per cent (95% CI: 14-34%) in the ASSA2003 model. Both models also estimated a small reduction in incidence owing to antiretroviral treatment by 2008. Increased condom use therefore appears to be the most significant factor explaining the recent South African HIV incidence decline.
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Rates of HIV testing and diagnosis in South Africa: successes and challenges
Background: UNAIDS aims for 90% of HIV-positive individuals to be diagnosed by 2020, but few attempts have been made in developing countries to estimate the fraction of the HIV-positive population that has been diagnosed.
Methods: To estimate the rate of HIV diagnosis in South Africa, reported numbers of HIV tests performed in the South African public and private health sectors were aggregated, and estimates of HIV prevalence in individuals tested for HIV were combined. The data were integrated into a mathematical model of the South African HIV epidemic, which was additionally calibrated to estimates of the fraction of the population ever tested for HIV, as reported in three national household surveys.
Results: The fraction of HIV-positive adults who were undiagnosed declined from more than 80% in the early 2000s to 23.7% [95% confidence interval (95% CI) 23.1 - 24.3] in 2012. The undiagnosed proportion in 2012 was substantially higher in men (31.9%, 95% CI 29.7 - 34.3) than in women (19.0%, 95% CI 17.9 - 19.9).
Conclusion: South Africa has made significant progress in expanding access to HIV testing, and at current testing rates, the target of 90% of HIV-positive adults diagnosed by 2020 is likely to be reached. However, uptake is relatively low in men and older adults.