September 2012

Published on September 12, 2012 by

Editorial

AIDS 2012 has come and gone. South African researchers and NGOs engaged in AIDS related work were ever visible, presenting new results, chairing key sessions, or delivering invited talks. Before the conference began, it was widely noted that an important shift in debate has occurred in recent years, concerning the coalescence of treatment and prevention. The real discussion is now much more about how, practically, to access the prevention benefit of treatment. This debate, at AIDS 2012, although heated at times, at least did not just go over the same old ground. Furthermore, the progress here has largely been based on the work of South Africans pushing these ideas, and amassing the evidence of early impact of our local treatment programme. It must be said that South Africans are doing some of the most important work in many aspects of HIV research, not just in applications to our specific problems, but also raising the bar internationally in the practice of good science.

Published on September 12, 2012 by

Can regular measurements of HIV concentration in blood during antiretroviral therapy prevent transmission?

A recent randomized controlled trial demonstrated that antiretroviral therapy (ART) prevents HIV transmission. In successfully treated patients the HI virus in the blood is suppressed to undetectable levels and therefore the probability of transmitting the virus is extremely low. This new finding must be incorporated into the evaluation of the advantages and disadvantages of different ART provision strategies. The optimal strategy for monitoring treatment response and detecting treatment failure – routine viral load monitoring (rVL) or CD4 cell counts or clinical symptoms – has been the subject of continuous debate. We suspected that rVL could potentially prevent HIV transmission by making it easier to detect treatment failure earlier. We developed a mathematical simulation model to estimate potential transmission from 1,000 patients treated with ART with either rVL or CD4 monitoring.

Published on September 12, 2012 by

Challenges to quantitative modelling of cholera disease transmission

Outbreaks of cholera are ongoing, with recent outbreaks in Zimbabwe and Haiti highlighting the devastation this disease can cause. In response, several mathematical models of cholera transmission have been proposed, with the aim of comparing the impact of interventions including provision of clean water, antibiotics, and vaccination. In this piece, we provide a brief summary of how uncertainty in parameters and the spatial heterogeneity of cholera incidence argue for cautious interpretation of quantitative predictions about the impact of interventions.

Published on September 12, 2012 by

The use of clusters to estimate recent transmission of TB

A new case of TB is the outcome of a recent infection event (primary TB) or is the result of the reactivation of a latent infection acquired some years previously. In a community where TB is endemic it is important to know the extent to which primary cases contribute to the overall burden as this can inform strategies to deal with the epidemic. This article discusses the methods for estimating the proportion of cases due to recent transmission by using cluster analysis. Sputum specimens from cases reporting to clinics are cultured and the TB strains are identified, commonly using molecular techniques of DNA ‘fingerprinting’. By comparing these fingerprints from various patients it becomes possible to classify them as unique or clustered. The proportion of clustered individuals can then be used as an indicator of the proportion of on-going or recent transmission.