Dr Leigh Johnson will present the Department of Statistical Science seminar with a talk entitled, "A Bayesian approach to understanding adult mortality trends in South Africa and the impact of antiretroviral treatment".

Dr Leigh Johnson is an epidemiologist and actuary, with an interest in the modelling of HIV and other sexually transmitted infections. He has been involved in evaluating the impact of a range of HIV prevention and treatment programmes in South Africa. His work includes estimating the demographic impact of HIV/AIDS in South Africa, and he has been involved in the development of the Actuarial Society of South Africa AIDS and Demographic model.

Abstract: Adult mortality rates in South Africa increased substantially over the period from 1997 to 2006, but have since declined steadily. Although this decline is often attributed to the success of antiretroviral treatment (ART) in reducing HIV-related mortality, there have been no formal attempts to quantify the extent to which ART explains the observed reduction. In this study we perform a Bayesian evidence synthesis, combining South African recorded death data, HIV prevalence data, reported numbers of ART patients and ART mortality rates within a mathematical modelling framework. The objectives of this study are to assess the extent to which ART has reduced adult mortality in South Africa, and to assess the role of other factors – such as changes in HIV virulence – in the observed mortality decline. In addition, this study aims to assess the value of recorded death data in the calibration of HIV models, which have previously been calibrated only to HIV prevalence data, and to evaluate the extent to which different HIV data sources are in conflict.