In 2014, the World Health Organization convened the  Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER) Working Group, with the aim to define and promote good practice in reporting global health estimates .The GATHER Statement is the outcome produced by this group, further outlined on their website at This statement defines a list of minimum reporting requirements to allow for the accurate interpretation, and facilitate the appropriate use, of global health estimates – applicable to HIV estimates reported by UNAIDS in collaboration with the UNAIDS Reference Group. Both UNAIDS and the UNAIDS Reference Group wholly endorse the GATHER Statement and seeks to be fully compliant with their recommendations.

Results from the UNAIDS 2016 estimates are available on their website (, and are presented in multiple formats, namely:

  • Country, regional and global estimates are available at

  • a quick fact sheet on global HIV statistics

  • a spreadsheet containing the HIV estimates with uncertainty bounds

  • Reports explaining the significance of results, e.g. Prevention GAP report 2016 summarising the results

  • Country specific Spectrum files used to develop the estimates are available upon request at

The fulfilment of the GATHER criteria for the 2016 estimates have been listed in the table below.

GATHER checklist item (abbreviated) Evidence of compliance Status
1. Define indicators, population and time period of estimates The estimates and their metadata are available from under the sections people living with HIV, New HIV infections, AIDS deaths, orphans, ART coverage and PMTCT coverage. Met
2. Funding sources UNAIDS; US Government; Global Fund for AIDS, Malaria and Tuberculosis; Bill and Melinda Gates Foundation Met
3. How data inputs were accessed Data are compiled by country HIV estimates teams from program records and surveillance systems Met
4. Inclusion and exclusion criteria All survey and surveillance data are used in each country unless there are known data quality issues, very short time series (surveillance data), or response rates are so low that findings are likely to be biased (national surveys). All available program data are used (number of ART and PMTCT patients) after validation by country teams and global partners More detail required than can be provided here
5. Data sources and references, diagnostic methods, sample size Prevalence and incidence trends are based on surveillance and survey data. Surveillance data include HIV prevalence measured at ante-natal clinics as well as surveillance conducted among key populations (sex workers, clients, men who have sex with men, people who inject drugs) and any additional groups relevant to a country’s epidemic for which data are available. Sample sizes are typically 300 – 500 per site. National surveys of HIV prevalence are available for some countries and usually include sample sizes of 5,000 – 45,000. The sample sizes for each survey or study are included in the software. Testing is conducted according to standard HIV testing protocols with confirmatory tests for HIV positives. Met
6. Identify and describe any categories of input data that have potentially important biases Numbers of people receiving antiretroviral medicines or therapy could be undercounted if not all sites have reported by the time of estimates development or might by double counted if de-duplication efforts are not feasible or not conducted. Prevalence trends among pregnant women are not necessarily representative of the total population. Mortality data used to calibrate incidence curves might be under reported due to stigma related to AIDS deaths. Survey measures of prevalence may be biased if refusal rates are high or if testing algorithms were not accurately implemented. More detail required than can be provided here
7. Additional data sources Parameters for generalized epidemics are based primarily on demographic surveillance sites in eastern and southern Africa. Survival on ART is based on data from IeDEA consortium sites which might not be representative of all public providers. More detail required than can be provided here
8. All data inputs are available Complete files with all input data can be downloaded from For those country files not publicly available, country team contact details can be requested from UNAIDS. Met
9. Conceptual overview of the methods See Spectrum Quickstart guide and Spectrum manual at
Models are also fully described in published articles: [1-9]
10. Description of the steps Quickstart guide describing steps to create the estimate files is available from Met
11. How were candidate models evaluated See meeting reports at Met
12. Results of model evaluations and sensitivity analyses See meeting reports at Met
13. Methods for calculating uncertainty The following articles describe the methods for calculating uncertainty:[2,3] Met
14. How to access code Code can be requested from Avenir Health and East-West Center. Being documented
15. Access to results See Met
16. Access to uncertainty results See Met
17. Interpretation of results in addition to other evidence and changes See latest UNAIDS publications at Met
18. Limitations of the estimates As of mid-2016 a selection of the limitations include:
Incidence by age and sex is based on assumptions from cohort studies and might not reflect the situation in individual countries.
For concentrated epidemics estimates of sizes of key populations may not match the population in which surveillance is conducted making it difficult to estimate the total population of people living with HIV.
In generalized epidemics information on prevalence among children is only available for a few countries against which to validate and compare the modelled estimates.
Information on distribution of ART by age and sex is limited in most countries. Fertility patterns among women living with HIV (especially in concentrated epidemics) are not available reducing the ability to accurately estimate children exposed and potentially infected with HIV.
More detail required than can be provided here


  1.  Stover J, Walker N, Grassly NC, Marston M. Projecting the demographic impact of AIDS and the number of people in need of treatment: updates to the Spectrum projection package. Sex Transm Infect. 2006 Jun;82 Suppl 3:iii45-50.
  2.  Stover J, Johnson P, Zaba B, Zwahlen M, Dabis F, Ekpini RE. The Spectrum projection package: improvements in estimating mortality, ART needs, PMTCT impact and uncertainty bounds. Sex Transm Infect. 2008 Aug;84 Suppl 1(1):i24-i30.
  3.  Brown T, Bao L, Raftery AE, Salomon JA, Baggaley RF, Stover J, et al. Modelling HIV epidemics in the antiretroviral era: the UNAIDS Estimation and Projection package 2009. Sex Trans Infect. 2010 December 1, 2010;86(Suppl 2):ii3-ii10.
  4. Stover J, Johnson P, Hallett T, Marston M, Becquet R, Timaeus IM. The Spectrum projection package: improvements in estimating incidence by age and sex, mother-to-child transmission, HIV progression in children and double orphans. Sex Trans Infect. 2010 December 1, 2010;86(Suppl 2):ii16-ii21.
  5. Hogan DR, Salomon JA. Spline-based modelling of trends in the force of HIV infection, with application to the UNAIDS Estimation and Projection Package. Sex Transm Infect. 2012 Dec;88 Suppl 2:i52-7.
  6. Bao L, Salomon JA, Brown T, Raftery AE, Hogan DR. Modelling national HIV/AIDS epidemics: revised approach in the UNAIDS Estimation and Projection Package 2011. Sex Transm Infect. 2012 Dec;88 Suppl 2:i3-10.
  7. Stover J, Brown T, Marston M. Updates to the Spectrum/Estimation and Projection Package (EPP) model to estimate HIV trends for adults and children. Sex Transm Infect. 2012 Dec;88 Suppl 2:i11-6.
  8. Brown T, Bao L, Eaton JW, Hogan DR, Mahy M, Marsh K, et al. Improvements in prevalence trend fitting and incidence estimation in EPP 2013. AIDS. 2014;28:S415-S25.
  9. Stover J, Andreev K, Slaymaker E, Gopalappa C, Sabin K, Velasquez C, et al. Updates to the spectrum model to estimate key HIV indicators for adults and children. AIDS. 2014 Nov;28 Suppl 4:S427-34.