HIV prevalence among adults aged ≥15 years

Rate

HIV and AIDS has become a major public health problem in many countries and monitoring the course of the epidemic and impact of interventions is crucial. Both the Millennium Development Goals (MDG) and the United Nations General Assembly Special Session on HIV and AIDS (UNGASS) have set goals of reducing HIV prevalence.

The estimated number of adults aged 15 years and over with HIV infection, whether or not they have developed symptoms of AIDS, per 100 000 population of the same age group.

Sex, Location (urban/rural), Boundaries : Administrative regions, Boundaries : Health regions

Standardized tools and methods of estimation have been developed by UNAIDS and WHO in collaboration with the UNAIDS Reference Group on Estimation, Modelling and Projections.   In countries with a generalized epidemic, national estimates of HIV prevalence are based on data generated by surveillance systems that focus on pregnant women who attend a selected number of sentinel antenatal clinics, and in an increasing number of countries on nationally representative serosurveys. In countries with a low level or concentrated epidemic national estimates of HIV prevalence are primarily based on surveillance data collected from populations at high risk (sex workers, men who have sex with men, injecting drug users) and estimates of the size of populations at high and low risk. This data is entered into the Estimation and Projection Package (EPP) software  which fits a simple epidemiological model to the epidemic structure defined. EPP finds the best fitting curve that describes the evolution of adult HIV prevalence over time, and calibrates that curve based on prevalence found in any national surveys or default values in case there is no national survey available.  For countries with very little available prevalence data (less than three consistent surveillance sites) a point prevalence estimate and projection is made using spreadsheet models (the Workbook Method). The resulting point prevalence estimates for several years are entered into EPP to find the best fitting curve that describes the evolution of adult HIV prevalence over time.   (http://www.unaids.org/en/KnowledgeCentre/HIVData/Methodology/ , accessed on 15 April 2009)

Impact

The country-specific estimates of adults living with HIV, used as the numerator for this indicator, have been produced by National AIDS Programs and compiled by UNAIDS and WHO. They have been discussed  with national AIDS programs for review and comments, but are not necessarily the official estimates used by national governments. For countries where no recent data were available, country-specific estimates have not been listed in the tables. (2008 Report on the Global AIDS epidemics, Annex 1).   The population estimates, used as the denominator by WHO to calculate the prevalence per 100 000 population, are those published by the United Nations Population Division, 2006 revision.   Predominant type of statistics: predicted

Regional estimates are weighted averages of the country data, using the number of population aged ≥ 15 years for the reference year in each country as the weight. No figures are reported if less than 50 per cent of the population aged ≥ 15 years in the region are covered.

Cases per 100 000 population (of the respective age group)

Biennial (Two years)

For this indicator, adults are defined as men and women aged 15 years and over. This is different from previous reports where the estimates for adults were restricted to 15–49-year-olds. Since the burden of disease extends beyond the age of 49 and to better assess that need, the UNAIDS Reference Group on Estimates, Modelling and Projections has recommended changing the reporting to all ages. The estimates in the 2008 Report on the Global AIDS epidemics are presented together with ranges, which reflect the certainty associated with each of the estimates. The extent of uncertainty depends mainly on the type of epidemic, and the quality, coverage and consistency of a country’s surveillance system and, in generalized epidemics, whether or not a population-based survey with HIV testing was conducted. (2008 Report on the Global AIDS epidemics, Annex 1) The main indicator proposed for monitoring progress towards achieving the international goals is HIV prevalence among young people aged 15-24 years, which is a better proxy for monitoring HIV incidence.  Although countries are moving towards collecting better data on young people, mainly by capturing data on young pregnant women attending antenatal clinics or national population based surveys, comparable data availability is still limited. Analysis of trends on consistent sites have been proposed as a an alternative to tool to assess recent rends and countries have been encouraged to collect report HIV surveillance data by age breakdown.