March 2013

Published on March 18, 2013 by

Editorial: Statistical and epidemiological modelling towards Maximizing ART for Better Health and Zero New HIV Infections

The contributions in this issue of the SACEMA Quarterly focus on different aspects related to TB and incidence of HIV. This editorial focuses on HIV treatment as prevention by presenting the MaxART project (Maximizing ART for Better Health and Zero New HIV Infections). This project pursues the dream of reaching all people in Swaziland who are in need of treatment with an ultimate goal of preparing the country for the possibility of ending the HIV epidemic. SACEMA is one of the members of the MaxART consortium and is involved in various modelling and analysis activities that are presented here.

Published on March 18, 2013 by

Sputum smear-positive tuberculosis among previously treated individuals in the Western Cape Province, South Africa

A considerable share of South Africa’s tuberculosis burden affects those people who have previously been treated for tuberculosis – many of them successfully. In a retrospective cohort study that was conducted using tuberculosis treatment register data from two communities in suburban Cape Town, it was found that the hazard rate of re-treatment for smear-positive tuberculosis was between 3- and 5.26-times higher in tuberculosis cases who had defaulted from treatment compared to successfully treated cases. But although the rate of re-treatment was substantially higher among defaulters, cases after treatment success account for the vast majority of smear-positive re-treatment cases due to the fact that far more tuberculosis cases were successfully treated than had defaulted.

Published on March 18, 2013 by

Oscillating Migration Driving HIV and TB in sub-Saharan Africa

The system of oscillating labour migration, especially to the gold mines in South Africa, has helped to spread TB throughout southern Africa and it now helps to spread HIV. This article illustrates this link by reporting on a study on the impact of migrant labour in the mines in South Africa on the burden of HIV and TB in Mozambique. Furthermore, modelling studies have shown that even if we maintain the same patterns of sexual behaviour the presence or absence of migration can lead to dramatically different outcomes. Unless a comprehensive and fully coordinated multi-country and multi-sectoral programme is implemented and followed through, we may find that the HIV and TB epidemics are far more resilient than consideration of the epidemics in each country suggests.

Published on March 18, 2013 by

Different ways to estimate the mean duration of “recent HIV infection” as measured by the BED assay

Robust affordable means for estimating HIV incidence at the population level continue to be elusive and much desired. As resources are invested in developing more appropriate tests for recent infection, the methods for evaluating and optimising the performance of candidate tests need to be further refined. We have recently explored a range of statistical methods for estimating the mean duration of recent infection (MDRI) by investigating a data set from Harare, Zimbabwe. We investigated whether there is an optimum way of estimating the mean recency duration for this dataset. We also ask how estimates of the mean recency duration and incidence are affected by our choice of cut-off and whether these effects differ with our choice of estimation method.

Short item Published on March 18, 2013

Understanding TB latency using computational and dynamic modelling procedures

The Mycobacterium tuberculosis (TB) bacilli’s potency to cause persistent latent infection that is unresponsive to the current cocktail of TB drugs is strongly associated with its ability to adapt to changing intracellular environments, and tolerating, evading and subverting host defence mechanisms. We applied a combination of bioinformatics and mathematical modelling methods to enhance the understanding Read More

Short item Published on March 18, 2013

Biology as Population Dynamics: Heuristics for Transmission Risk

Population-type models, accounting for phenomena such as population lifetimes, mixing patterns, recruitment patterns, genetic evolution and environmental conditions, can be usefully applied to the biology of HIV infection and viral replication.  A simple dynamic model can explore the effect of a vaccine-like stimulus on the mortality and infectiousness, which formally looks like fertility, of invading Read More

Short item Published on March 18, 2013

Video: Brian Williams addresses U.S. Senators, Congress Members and Staff on Test-and-Treat

On June 19, 2012, SACEMA’s Brian Williams, also Senior Technical Adviser to Test & Treat to End AIDS, held a briefing in Washington DC in which he explained to US senators, members of congress, and staff how this strategy has the potential to stop the spread of HIV/AIDS and, over time, to save billions of Read More

Short item Published on March 18, 2013

Have the explosive HIV epidemics in sub-Saharan Africa been driven by higher community viral load?

In contrast with the other regions, HIV infection in sub-Saharan Africa (SSA) is prevalent in the general population with low levels of reported sexual risk behaviours. SSA bears also the highest burden of infectious diseases other than HIV such as malaria, tuberculosis, herpes simplex virus type 2, among other infectious diseases. The drivers of the Read More

Short item Published on March 18, 2013

Clinic on the Meaningful Modelling of Epidemiological Data

The South African Centre for Epidemiological Modelling (SACEMA) invites applications to the fourth annual Clinic on the Meaningful Modelling of Epidemiological Data. This two-week modelling clinic, mounted in collaboration with the International Clinics on Infectious Disease Dynamics and Data (ICI3D) Program, and the African Institute for Mathematical Sciences (AIMS), will emphasize the use of data in understanding Read More