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Updated: Jun 28, 2026

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses
Published on: February 22, 2019
Life histories of pathogen populations
1Department of Pediatrics, The University of Chicago, 5841 S. Maryland Ave., MC 5058, Chicago, IL 60637, USA. addresses: r-perlman@uchicago.edu
Abstract:
The populations of pathogens in individual hosts have many of the characteristics of multicellular organisms, or individuals. These populations go through a life cycle within a host and they reproduce by founding daughter populations in new hosts. Natural selection shapes the life history characteristics of pathogen populations--life expectancy, trade-offs in the allocation of resources between growth, survival, and fecundity, and aging--in ways that maximize the reproductive fitness of the pathogens. In turn, these life history characteristics shape the natural histories of infectious diseases. Transmissibility and virulence may be thought of as properties of pathogen populations rather than as properties of the constituent microorganisms within these populations. The poor correlation of virulence with pathogen fitness is a major obstacle to the development of a theory of virulence. Consideration of the life histories of pathogen populations complements the traditional epidemiological focus on host populations and provides a valuable perspective for understanding human infectious diseases.
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