Origins of HIV and the AIDS Epidemic [Discussion Meeting (2000: London, England)]

same geographical patterns as mitochondrial variation. The minimal sampling of wild chimpanzee
populations across Africa for SIV and lack of knowledge about epidemiology do not seem to allow the
exclusion of populations in other locations as potential host of the SIV ancestor of HIV1. The history of
human-chimpanzee contacts is discussed.
Infectious disease dynamics: What characterises a successful invader?
Professor Robert M May AC FRS
University of Oxford, UK
Against the background of HIV/AIDS and other potentially emerging (or re-emerging) infectious diseases, this
talk will focus on the properties which enable an infectious agent to establish and maintain itself within a
specified host population. I will emphasise that for a pathogen to cross a species barrier is one thing, but for
it successfully to maintain itself in the new population it must have a "basic reproductive number", R0, which
satisfies Ro > 1. I will further discuss how behavioural factors interweave with the basic biology of the
production of transmission stages by the pathogen, all subject to possible secular changes, to determine the
magnitude of R0. Although primarily focused on HIV/AIDS, I will review wider aspects of these questions.
Serial human passage of SIV: the role of unsterile injecting emergence of epidemic strains of HIV
Dr Preston A Marx, Philip G Alcabes and Ernest Drucker
Tulane Regional Primate Research Center, USA
Compelling evidence exists that both human immunodeficiency virus (HIV) types 1 and 2 emerged from
dissimilar simian immunodeficiency viruses (SIVs) in separate geographical regions of Africa. The natural
simian hosts of SIV have been in close contact with humans for thousands of years without the emergence
of epidemic HIV. There is therefore, no plausible explanation for the sudden emergence of multiple epidemic
HIVs in the 20th century. We have studied the massive use of unsterilized needles in Africa in the 20th
century as the key factor in the emergence of epidemic HIV from weakly pathogenic SIV crossover infections.
We propose that SIV was genetically adapted to humans by serial human passage of SIV by unsterilized
needles. This mechanism provides a plausible and parsimonious explanation for the nearly simultaneous
emergence of two distinct HIV epidemics in widely separate regions of Africa.
The burden of proof and the origin of AIDS
Dr Brian Martin
University of Wollongong, Australia
There is a distinct difference in the way that different theories about the origin of AIDS have been treated,
with the widely supported cut-hunter theory given relatively little scrutiny while the oral-polio-vaccine theory
has been subject to intense criticism. This difference in treatment cannot be explained as application of the
scientific method. A better explanation is that the burden of proof is put on all contenders to the cut-hunter
theory, giving it an unfair advantage, especially given that this assignment of the burden of proof appears to
reflect nonscientific factors.