This cross-sectional study examined whether sexual risk taking behaviours were impacted by knowledge of partner HIV status among HIV-infected South Africans enrolled in a primary care program. The study assessed four self-reported sexual risk behaviours as outcomes, namely current partner HIV status, reporting >2 sex acts in the last 2 weeks, reporting unprotected sex in Read More
An article published in the Journal of Theoretical Biology considered an HIV/AIDS model in the presence of an HIV testing and screening campaign (1). Reduction of new HIV infections by implementing a comprehensive national HIV prevention programme at a sufficient scale to have real impact remains a priority. The formulated model is analyzed and fitted Read More
Initiation of antiretroviral treatment (ART) is guided by a CD4 count and the current WHO guidelines recommend a CD4 count of 350 cells/mm3 as the threshold. In resource poor settings, traditional flow cytometric CD4 counting facilities are not widely available due to high costs and the infrastructure required. In these cases they rely on clinical Read More
The 6th IAS conference was held from 17-20 July 2011 in Rome. Although the conference is on HIV pathogenesis, treatment & prevention, the main focus this year was on the role of treatment in prevention. This prevention strategy can take different forms. First, by the immediate initiation of antiretroviral therapy (ART) after an HIV positive diagnosis, with a view to reducing a patient’s viral load and hence infectiousness. A second option is the use of a microbicide containing an antiretroviral, to reduce the probability of HIV negative people becoming infected. Finally, treatment as prevention can take the form of pre-exposure prophylaxis (PrEP) whereby antiretrovirals are used by individuals at high risk of exposure to HIV infection. The interim results of the FEM-PrEP trial showed that Truvada does not have a protective effect in women. But at the IAS conference the results of two new studies (the Partners PrEP trial and the TDF2 trial) on the use of oral PrEP in heterosexual people were extensively discussed. For these trials it was estimated that PrEP reduced the risk of transmission by between 62 and 78%.
Transmission of tuberculosis (TB) involves random processes operating at two very different levels. On the one hand, an infectious person must be in reasonably close proximity to a susceptible person for a minimum period of time (macro-level). On the other hand, minute droplets containing bacteria entities that are exhaled by the infectious person are inhaled by the recipient (micro-level). At both these levels the chance events can be described by a statistical formula, the Poisson distribution. An analysis of these two processes in this way reveals a surprising phenomenon that manifests in communities experiencing high incidences of TB disease.
Living in single-sex hostels, separated from their girlfriends, wives and children, and with few or no alternative to turn to, binge drinking and commercial or sex are common choices for recreation among mineworkers in Southern Africa. Binge drinking facilitates the acquisition and transmission of HIV and other sexually transmitted infections due to increased sexual risk behaviour. To explore the potential of preventing new HIV infections among mineworkers by reducing binge drinking in this population, a mathematical model was developed that aims to capture the causal associations between binge drinking, sexual risk behaviours and HIV incidence.
Most multivariable models in clinical and epidemiology research consider predictor variables as linear terms or as dummy variables after categorization of continuous variables. Clinically it may be desirable to classify patients into different prognosis groups, but categorization of continuous variables assumes homogeneity of the trait under consideration within each specified category. This may however be unrealistic especially when few categories are used. Categorization may result in overparameterized models and there is usually loss of efficiency. Important relevant predictor variables are sometimes missed in prognostic or diagnostic models because the true functional form of a predictor variable may be non-linear. Categorizing confounding variables may result in residual confounding. Fractional polynomials have been proposed in epidemiological studies to investigate functional forms of continuous predictor variables and confounders.