Modelling HIV epidemics in the antiretroviral era: the UNAIDS Estimation and Projection package 2009

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Abstract

Objective

The UNAIDS Estimation and Projection Package (EPP) is a tool for country-level estimation and short-term projection of HIV/AIDS epidemics based on fitting observed HIV surveillance data on prevalence. This paper describes the adaptations made in EPP 2009, the latest version of this tool, as new issues have arisen in the global response, in particular the global expansion of antiretroviral therapy (ART).

Results

By December 2008 over 4 million people globally were receiving ART, substantially improving their survival. EPP 2009 required modifications to correctly adjust for the effects of ART on incidence and the resulting increases in HIV prevalence in populations with high ART coverage. Because changing incidence is a better indicator of program impact, the 2009 series of UNAIDS tools also focuses on calculating incidence alongside prevalence. Other changes made in EPP 2009 include: an improved procedure, incremental mixture importance sampling, for efficiently generating more accurate uncertainty estimates; provisions to vary the urban/rural population ratios in generalised epidemics over time; introduction of a modified epidemic model that accommodates behaviour change in low incidence settings; and improved procedures for calibrating models. This paper describes these changes in detail, and discusses anticipated future changes in the next version of EPP.

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Time from HIV seroconversion to death: a collaborative analysis of eight studies in six low and middle-income countries before highly active antiretroviral therapy.

Etienne Karita, Ram Rangsin, T. Nelson … (2007)

To estimate survival patterns after HIV infection in adults in low and middle-income countries. An analysis of pooled data from eight different studies in six countries. HIV seroconverters were included from eight studies (three population-based, two occupational, and three clinic cohorts) if they were at least 15 years of age, and had no more than 4 years between the last HIV-negative and subsequent HIV-positive test. Four strata were defined: East African cohorts; South African miners cohort; Thai cohorts; Haitian clinic cohort. Kaplan-Meier functions were used to estimate survival patterns, and Weibull distributions were used to model and extend survival estimates. Analyses examined the effect of site, age, and sex on survival. From 3823 eligible seroconverters, 1079 deaths were observed in 19 671 person-years of follow-up. Survival times varied by age and by study site. Adjusting to age 25-29 years at seroconversion, the median survival was longer in South African miners: 11.6 years [95% confidence interval (CI) 9.8-13.7] and East African cohorts: 11.1 years (95% CI 8.7-14.2) than in Haiti: 8.3 years (95% CI 3.2-21.4) and Thailand: 7.5 years (95% CI 5.4-10.4). Survival was similar for men and women, after adjustment for age at seroconversion and site. Without antiretroviral therapy, overall survival after HIV infection in African cohorts was similar to survival in high-income countries, with a similar pattern of faster progression at older ages at seroconversion. Survival appears to be significantly worse in Thailand where other, unmeasured factors may affect progression.

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The UNAIDS Estimation and Projection Package: a software package to estimate and project national HIV epidemics.

K Stanecki, Lori Stover, Matthew Brown … (2004)

This paper describes the Estimation and Projection Package (EPP) for estimating and projecting HIV prevalence levels in countries with generalised epidemics. The paper gives an overall summary of the software and interface. It describes the process of defining and modelling a national epidemic in terms of locally relevant sub-epidemics and the four epidemiological parameters used to fit a curve to produce the prevalence trends in the epidemic. It also provides an example of using the EPP in a country with a generalised epidemic. The paper discusses the strengths and weaknesses of the software and its envisaged future developments.

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National population based HIV prevalence surveys in sub-Saharan Africa: results and implications for HIV and AIDS estimates.

Israel J. P. Garcia, E. Jeanne Gouws, Peter D. Ghys (2006)

Sentinel surveillance among pregnant women attending antenatal clinics (ANCs) has been the main source of information on HIV trends in sub-Saharan Africa. These data have also been used to generate national HIV and AIDS estimates. New technologies and resources have allowed many countries to conduct national population based surveys that include HIV prevalence measurement, as an additional source of information on the AIDS epidemic. The authors reviewed the reports of 20 national population based surveys from 19 countries carried out in sub-Saharan Africa since 2001. They examined the sampling methodology, HIV testing and response rates, and female:male and urban:rural prevalence ratios. They also constructed adjusted prevalence scenarios assuming different relative risks for survey non-responders. The national population based surveys vary considerably in quality, as reflected in the household response rate (ranging from 75.4% to 99.7%), women's testing rate (ranging from 68.2% to 97.3%), and men's testing rate (ranging from 62.2% to 95.4%), while for some surveys detailed response information is lacking. While 95% confidence intervals around the female:male and urban:rural prevalence ratios in individual countries are large, the median female:male ratio of the combined set of surveys results is 1.5 and the median urban:rural ratio 1.7. A scenario assuming that non-responders have twice the HIV prevalence of those who fully participated in the survey suggests that individual non-response could result in an adjusted HIV prevalence 1.03 to 1.34 times higher than the observed prevalence. Population based surveys can provide useful information on HIV prevalence levels and distribution. This information is being used to improve national HIV and AIDS estimates. Further refinements in data collection, analysis, and reporting, combined with high participation rates, can further improve HIV and AIDS estimates at national and regional level.

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Author and article information

Journal

Journal ID (nlm-ta): Sex Transm Infect

Journal ID (publisher-id): sti

Journal ID (hwp): sextrans

Title: Sexually Transmitted Infections

Publisher: BMJ Group (BMA House, Tavistock Square, London, WC1H 9JR )

ISSN (Print): 1368-4973

ISSN (Electronic): 1472-3263

Publication date (Electronic): 23 November 2010

Publication date (Print): December 2010

Publication date PMC-release: 23 November 2010

Volume: 86

Issue: Suppl_2 , The 2009 HIV and AIDS estimates and projections: methods, tools and analyses

Pages: ii3-ii10

Affiliations

[1 ]Population and Health Studies, East-West Center, Honolulu, Hawaii, USA

[2 ]Department of Statistics, University of Washington, Seattle, Washington, USA

[3 ]Harvard School of Public Health, Boston, Massachusetts, USA

[4 ]Department of Infectious Disease Epidemiology, Imperial College London, London, UK

[5 ]Futures Institute, Glastonbury, Connecticut, USA

[6 ]Population Division, Department of Economic and Social Affairs, New York, New York, USA

Author notes

Correspondence to Tim Brown, Population and Health Studies, East-West Center, 1601 East-West Road, Honolulu, HI 96848, USA; tim@ 123456hawaii.edu

Article

Publisher ID: sextrans44784

DOI: 10.1136/sti.2010.044784

PMC ID: 3173807

PubMed ID: 20929855

SO-VID: e64fad54-b77e-46cc-abca-851b17ce96f9

Copyright © © 2010, Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.

Modelling HIV epidemics in the antiretroviral era: the UNAIDS Estimation and Projection package 2009

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Abstract

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Most cited references 14

Time from HIV seroconversion to death: a collaborative analysis of eight studies in six low and middle-income countries before highly active antiretroviral therapy.

The UNAIDS Estimation and Projection Package: a software package to estimate and project national HIV epidemics.

National population based HIV prevalence surveys in sub-Saharan Africa: results and implications for HIV and AIDS estimates.

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