• HIV

Since 2004 we have provided detailed descriptions of the tools and assumptions used in generating HIV and AIDS estimates, as well as the data and analyses underpinning them.1–3 The UNAIDS Reference Group on Estimates, Modelling and Projections has continued to advise on the methods to be implemented in the Estimation and Projection Package (EPP) and the AIM module of Spectrum, which are used by countries, together with UNAIDS and WHO, in preparing national estimates. Discussions in this group have resulted in many of the new features in the 2009 versions of these estimation tools (see http://www.epidem.org for meeting reports). This supplement continues the tradition of publishing descriptions of the approaches used in HIV estimates so that they reflect new information and remain transparent.

The current supplement contains three types of papers. Five papers explain new estimation and modelling methods, assumptions about important parameter values and a description of software tools used in producing the 2009 HIV and AIDS estimates.4–8 They are followed by a description of the quality of HIV surveillance systems in low and middle income countries as of 2009,9 a country application of the new estimation software tools for Jamaica,10 four analytical papers building on the results of the new set of global estimates 11–14 and one on recent surveillance data15 which together provide insights into the impact of the AIDS epidemic and the effect of treatment and prevention interventions on the course of the epidemic. Finally, two papers look forward to some potential alternative models required to improve ways of modelling prevalence curves as HIV epidemics progress to new states.16 17