Historical Epistemology of the Concept of Virulence: Molecular, Ecological, and Evolutionary Perspectives on Emerging Infectious Diseases in the 19th and 20th Century
Thesis or dissertation
University of Exeter
Reason for embargo
I need time to arrange publication of my research.
This thesis focuses on the trajectory of the biomedical concept of virulence from 1880 until the present. Following the concept across disciplinary boundaries, from a longue durée history perspective, it explores how virulence was shaped through two distinct, although sometimes overlapping, “styles of reasoning”. Located at the intersection of several distinct research domains in biology and medicine, the concept of virulence provides, in addition, a window into the complex and changing relations between evolutionary biology and the health sciences (broadly construed) over the past two centuries. Moving back and forth between field experiments and the laboratory, this work examines, through the lens of historical epistemology, the emergence of what I call the molecular and the ecological styles, and their respective conceptual practices. It focuses on the ways in which these styles operationalize the distinction between virulent or avirulent organisms in sometimes opposite sense: Whereas in the molecular (or endogenous) style the expression of virulence is explained by properties of internal structures of the infectious agent (e.g. polysaccharide capsule, virulence gene, or pathogenicity island), the concept of virulence in the ecological (or exogenous) style reflects, in contrast, either a lack of adaptation between two species (avirulence hypothesis) or the existence of one or more ecological compromises between, say, the mode of transmission of a pathogen and its host’s recovery rate (trade-off model). Both styles can be said to originate in the medical bacteriology of the late-nineteenth century, but while the former grew mostly out of the work of Louis Pasteur and Robert Koch in Europe, the latter was primarily shaped by Theobald Smith in the United States. Nearly a century later, the introduction of the category of emerging infectious disease within public health discourses in the mid-1990s facilitated a rapprochement between the two styles that had, so far, remained apart. Employing the 1918–1919 influenza pandemic as an example in which to illustrate the trajectory of the molecular and the ecological approaches, the diversity of explanatory schemes developed to account for the pandemic’s exceptional virulence points toward an unresolved, and yet productive, epistemic tension between the two styles, on the one hand, and the intrinsic polarity of the concept of virulence itself, on the other.
PhD in Philosophy
Social Sciences and Humanities Research Council of Canada, grant no 752-2007-1257.