Browsing by Author "Geffen, Nathan"
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- ItemOpen AccessAlgorithms for efficiently and effectively matching agents in microsimulations of sexually transmitted infections(2018) Geffen, Nathan; Kuttel, MichelleMathematical models of the HIV epidemic have been used to estimate incidence, prevalence and life-expectancy, as well the benefits and costs of public health interventions, such as the provision of antiretroviral treatment. Models of sexually transmitted infection epidemics attempt to account for varying levels of risk across a population based on diverse / or heterogeneous / sexual behaviour. Microsimulations are a type of model that can account for fine-grained heterogeneous sexual behaviour. This requires pairing individuals, or agents, into sexual partnerships whose distribution matches that of the population being studied, to the extent this is known. But pair-matching is computationally expensive. There is a need for computer algorithms that pair-match quickly. In this work we describe the role of modelling in responses to the South African HIV epidemic. We also chronicle a three-decade debate, greatly influenced since 2008 by a mathematical model, on the optimal time for people with HIV to start antiretroviral treatment. We then present and analyse several pair-matching algorithms, and compare them in a microsimulation of a fictitious STI. We find that there are algorithms, such as Cluster Shuffle Pair-Matching, that offer a good compromise between speed and approximating the distribution of sexual relationships of the study-population. An interesting further finding is that infection incidence decreases as population increases, all other things being equal. Whether this is an artefact of our methodology or a natural world phenomenon is unclear and a topic for further research.
- ItemRestrictedBeyond HAART: scientists and activists need to work together(Elsevier, 2009) Geffen, NathanThe two key barriers to obtaining AIDS drugs in South Africa until 2004 were the state’s support of AIDS denialism and high prices. The work of civil-society advocacy groups was essential to overcoming these barriers.1 The delayed roll-out of programmes for mother-tochild transmission prevention and for highly active antiretroviral treatment (HAART) conservatively resulted in 330 000 excess deaths.2,3 Nevertheless, AIDS activism helped reduce the price of antiretrovirals and change governmental policy, so that by mid-2008, 550 000 people were on HAART in South Africa, mostly in the public health system.
- ItemMetadata onlyCommunity views: balancing the public health benefits of earlier antiretroviral treatment with the implications for individual patients - perspectives from the community(Lippincott, Williams & Wilkins, 2014) Simon, Collins; Geffen, NathanPurpose of review: When should people with HIV start treatment? This question is widely debated. The recent momentum to initiate treatment at a CD4 cell count above 350 cells/mm3 is driven by the potential population benefits of antiretroviral treatment reducing infectiousness together with operational concerns. These are important. However, we focus on the clinical benefits and risks for the person taking treatment, and how this may vary depending on the background health setting. Recent findings: We refer to the recent guideline changes and the limited evidence on which they are based. Many studies that have informed guideline changes reference plausible benefits, but have limited follow-up and are not designed to assess the potential risks. We note historical examples to show that expert opinion in the absence of data warrants caution. Summary: Results from well powered studies designed to look at the question of when to start treatment are essential for quantifying the benefits and risks of earlier treatment. Meanwhile, the decision of when to start must be taken by the HIV-positive person in consultation with their health worker based on accurate information. That choice will vary depending on a person's individual health, their reason to want to treat and the resources of the health-care facility.
- ItemOpen AccessThe cost of HIV prevention and treatment interventions in South Africa(2003) Geffen, Nathan; Nattrass, Nicoli; Raubenheimer, ChrisThis paper estimates the costs of introducing several AIDS-related prevention and treatment programmes in South Africa.1 Our approach combines detailed information about the costs of implementing these interventions with demographic projections of their impact. Information about prices, wages and other cost components is drawn from a range of primary and secondary sources. Johnson and Dorrington’s (2002) modelling of the demographic impact of four AIDS-related health interventions is a central input into our costing exercise. We begin the paper with an overview of the key characteristics and results of their ASSA2000 ‘Interventions Model’.2 The paper then discusses the cost components of each of these interventions. We draw attention to the additional costs not considered in our primary analysis, and to the effect of antiretroviral medicine prices on the total cost of providing highly active antiretroviral therapy (HAART) to those who need it. HAART is expensive, but the net costs to government are significantly lower than the direct costs of providing HAART. This is because people on HAART experience fewer opportunistic infections (OIs) – thereby saving the government the costs of treating those OIs. We estimate these ‘hospital costs averted’, provide a brief discussion of the savings associated with fewer orphans, and then conclude with a calculation of the cost of prevention and treatment programmes as a percentage of GNP.
- ItemOpen AccessThe deadly hand of denial: Governance and politically-instigated AIDS denialism in South Africa(2009) Geffen, Nathan; Cameron, EdwinThe 26 May 2005 issue of Drum magazine, a widely-read South African monthly, featured a comparison of two deeply contrasting approaches to treating HIV. The strap-line was 'They both look the picture of health.? And they're both living with HIV/AIDS.? Yet Judge Edwin Cameron and Nozipho Bhengu each do it their way'. Bhengu, daughter of African National Congress (ANC) grandee, Ruth Bhengu (a close associate in exile of former President Thabo Mbeki), was, so the article claimed, controlling her infection and CD4 count with a nutritional concoction. 'Like [the former] health minister Manto Tshabala-Msimang', the article recorded, 'Nozipho believes there is a direct link between nutrition and AIDS'. An interview with one of the writers, Edwin Cameron, was posted alongside. Cameron explained how he was treating his HIV infection using scientifically proven antiretroviral (ARV) treatment. The article epitomised the fraught debate on HIV in South Africa at the time.
- ItemRestrictedEchoes of lysenko: state-sponsored pseudo-science in South Africa(Taylor & Francis, 2005) Geffen, NathanA major factor hampering the rollout of highly active antiretroviral treatment (HAART) for HIV/AIDS in the public health sector is state support of pseudoscience. This paper examines state-sponsored pseudo-science in South Africa with a particular focus on the case of Matthias Rath and his claim that HAART is an ineffective and harmful form of treatment and that multivitamins should instead be used as a substitute to treat and cure AIDS. The paper examines similarities and differences between state support in South Africa for AIDS-denialists such as Rath and state support in the former Soviet Union for Lysenko, a pseudo-scientist who lacked scientific training. In both cases, state support for pseudo-science has had policy implications, and resulted in many deaths.
- ItemOpen AccessEchoes of Lysenko: state-sponsored pseudo-science in South Africa(2006) Geffen, NathanA major factor hampering the rollout of highly active antiretroviral treatment (HAART) for HIV/AIDS in the public health sector is state support of pseudo-science. This paper examines state-sponsored pseudo-science in South Africa with a particular focus on the case of Matthias Rath and his claim that HAART is an ineffective and harmful form of treatment and that multivitamins should instead be used as a substitute to treat and cure AIDS.? The paper examines similarities and differences between state support in South Africa for AIDS-denialists such as Rath and state support in the former Soviet Union for Lysenko, a pseudo-scientist who lacked scientific training. In both cases, state support for pseudo-science has had policy implications, and resulted in many deaths.
- ItemOpen AccessEchoes of Lysenko: state-sponsored pseudo-science in South Africa(2006) Geffen, NathanA major factor hampering the rollout of highly active antiretroviral treatment (HAART) for HIV/AIDS in the public health sector is state support of pseudo-science. This paper examines state-sponsored pseudo-science in South Africa with a particular focus on the case of Matthias Rath and his claim that HAART is an ineffective and harmful form of treatment and that multivitamins should instead be used as a substitute to treat and cure AIDS.? The paper examines similarities and differences between state support in South Africa for AIDS-denialists such as Rath and state support in the former Soviet Union for Lysenko, a pseudo-scientist who lacked scientific training. In both cases, state support for pseudo-science has had policy implications, and resulted in many deaths.
- ItemOpen AccessEncouraging deadly choices: AIDS pseudo-science in the media(2007) Geffen, NathanThis article discusses the impact and ethics of media coverage on two forms of pseudo-science, namely HIV medical pseudo-science and environmental pseudo-science. The first section introduces some questions that should be raised when assessing the impact of reporting pseudo-science in the media. Coverage on environmental pseudo-science is discussed and contrasted with examples of a more deadly form of denial, HIV pseudo-science, in the second section of the article. The various arguments in support of freedom of information are evaluated in relation to the ethics of reporting HIV pseudo-scientific claims in the media, particularly given South Africa's burgeoning HIV epidemic. The final section of this article presents a number of practical recommendations for editors, journalists and scientists in order to provide an ethical framework for evaluating and covering potentially harmful pseudo-scientific claims in the media.?
- ItemRestrictedThe impact of reduced drug prices on the cost-effectiveness of HAART in South Africa(National Inquiry Services Centre, 2005) Nattrass, Nicoli; Geffen, NathanSouth Africa has started ‘rolling out’ highly active anti-retroviral therapy (HAART) through the public health sector, but implementation has been slow. Studies have shown that in Africa AIDS prevention may be more cost-effective than providing HAART; such published results provide some support for the South African government’s apparent reluctance to implement a large-scale rapid HAART roll-out. However, previous studies have not linked treatment and prevention plans, and do not, for the most part, consider the potential savings to the public health sector (e.g., fewer hospital admissions) that may arise from the introduction of HAART. The South African costing exercise summarised here avoids both these limitations. It provides an update of earlier work and takes into account the recent decline in antiretroviral drug prices. It shows that once HIV-related hospital costs are included in the calculation, the cost per HIV infection averted is lower in a treatment-plus-prevention intervention scenario than it is in a prevention-only scenario. This suggests that it is economically advantageous to fund a large-scale comprehensive intervention plan and that the constraints for doing so are political. Once human-rights considerations are included, the case for providing HAART is even more compelling.
- ItemRestrictedJustice After AIDS Denialism: Should There Be Prosecutions and Compensation?(Lippincott, Williams & Wilkins, 2009) Geffen, NathanEdward Mabunda died on April 9, 2003. At least another 600 people died of AIDS in South Africa that day.1 Edward was just 36 years old. He left behind a wife and 3 children. He was also a leader in the Treatment Action Campaign (TAC). He became an icon of the movement because of the fiery poetry that he recited to thousands of people. His poems urged former President Thabo Mbeki to make antiretrovirals (ARVs) available in South Africa’s public health system. He died because he could not obtain these life-saving medicines in time. From 1999 to 2007, Mbeki and his Minister of Health Manto Tshabalala-Msimang obstructed and then undermined the implementation of highly active ARV treatment (HAART) and prevention of mother-to-child transmission of HIV in the public health system. Two studies, conducted independently of each other, conservatively calculated that over 300,000 people died because of Mbeki’s AIDS denialist policies.3–5 Edward Mabunda was one of them. These studies could not account for additional deaths due to the promotion of quackery, often with the health minister’s support. They also did not consider the number of infections that occurred because of the confusion generated by the insipid state-funded prevention campaign and the messages by some outspoken Mbeki supporters dismissing the link between sex and HIV infection.6 The Mbeki era also fostered a profound mistrust of scientific medicine, the consequences of which also cannot be quantified.
- ItemOpen AccessPattern recognition and the nondeterminable affine parameter problem(1998) Geffen, Nathan; Mason, ScottThis thesis reports on the process of implementing pattern recognition systems using classification models such as artificial neural networks (ANNs) and algorithms whose theoretical foundations come from statistics. The issues involved in implementing several classification models and pre-processing operators - that are applied to patterns before classification takes place - are discussed and a methodology that is commonly used in developing pattern recognition systems is described. In addition, a number of pattern recognition systems for two image recognition problems that occur in the field of image matching have been developed. These image recognition problems and the issues involved in solving them are described in detail. Numerous experiments were carried out to test the accuracy and speed of the systems developed to solve these problems. These experiments and their results are also discussed.
- ItemOpen AccessProviding antiretroviral treatment for all who need it in South Africa(2003) Nattrass, Nicoli; Geffen, NathanIn August 2003, the South African government announced its support for the provision of highly active antiretroviral therapy (HAART) in the public sector. This was a major break-through (antiretrovirals are now explicitly recognised as beneficial) but the Cabinet statement was very cautiously worded about actual implementation. The Ministry of Health has been instructed to develop a 'detailed operational plan' but it is increasingly clear that one of the major constraints on the scale and pace of the roll-out will be the amount of resources allocated to it. Given the discourse of 'unaffordability' which has dogged South African AIDS policy making over the past five years (Nattrass, 2004 forthcoming) it is likely that South Africa will opt for a limited intervention on the grounds that resources are best spent elsewhere.
- ItemMetadata onlyWorld Health Organization guidelines should not change the CD4 count threshold for antiretroviral therapy initiation(AOSIS, South Africa, 2013) Geffen, NathanThe World Health Organization (WHO) currently recommends that HIV-positive adults start antiretroviral therapy (ART) at CD4 counts <350 cells/µl. Several countries have changed their guidelines to recommend ART irrespective of CD4 count or at a threshold of 500 CD4 cells/µl. Consequently, WHO is currently revising its treatment guidelines and considering recommending ART initiation at CD4 counts <500 cells/µl. Such decisions are critically important, as WHO guidelines inform healthcare policies in developing countries and are used by activists in their advocacy work. Changing the CD4 initiation point from 350 to 500 cells/µl would, however, be premature and have profound cost implications on Global Fund, President’s Emergency Plan for AIDS Relief (PEPFAR) and developing country health budgets. We should be willing to campaign for such a change in guidelines despite cost implications, if supported by evidence. However, the evidence remains outstanding.