Emory University - Population Biology, Ecology, & Evolution - Programs : Population biology of infectious disease

Population biology of infectious disease

Evolutionary genetics & molecular epidemiology
Within-host dynamics
Population dynamics & control
Evolution of drug resistance
Ecology of vector-borne & zoonotic diseases

Evolutionary genetics & molecular epidemiology
Host-pathogen interactions evolve as a consequence of ecological dynamics coupled with population genetic processes, such as natural selection and genetic drift. Our program hosts a variety of research foci directed at understanding the genetic basis of evolutionary change in host-pathogen interactions. Several labs are particularly interested in the evolution of antimicrobial resistance (an increasingly important public health issue) and its corollary, the evolutionary genetics of pathogen virulence and pathogenicity. The development of molecular tools to reveal vast amounts of sequence information has also increased our capacity to elucidate the evolutionary history of pathogens and the co-evolutionary dynamics between hosts and parasites. The modern field of molecular epidemiology uses these tools to uncover the phylogenetic history and origin of pathogens and patterns of disease emergence. Among a wide range of activities, our faculty and students have used these tools to discover the likely origins of syphilis, track the spread of rabies, expose the threats of Ebola in wildlife, and discover the origins of monkeypox outbreaks in Wisconsin.

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Within-host dynamics
Infections of vertebrate hosts can be thought of in terms of ecological, predator-prey type models with the pathogen being the prey and the immune response the predator. Proliferating and evolving populations of parasites stimulate the activation, proliferating and evolution of cells of the various branches of the immune system. These immune responses in turn control the pathogen population. These predator-prey type models can help us understand the dynamics of different infections and in particular understand: (i) how immune responses are generated, and long-lasting immunity maintained; (ii) why some pathogens (such as the measles virus and poliovirus) cause only short term infections while other pathogens (such HIV and HCV) can persist for extended periods of time; (iii) the role of antimicrobial agents and the immune system in the control of infections. A key aspect of the studies is to bring these models into close and potentially risky contact with experimental data.

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Population dynamics & control
Diseases often show predictable patterns of temporal reoccurrence or spatial spread from locations of initial emergence. Can we develop mathematical tools for describing patterns of spatial-temporal dynamics of infectious diseases, and how can we use these models to guide the development of vaccination, surveillance, and control measures? The faculty in this area often use large extant databases generated from world-wide surveillance and reporting programs to develop predictive theories of emergence and spread. The mathematical theories developed for disease of both humans and wildlife (e.g. rabies, influenza) also form the basis for mathematical modeling of the release of biological agents through acts of terrorism (e.g. smallpox, anthrax).

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Evolution of drug resistance
Evolution is not only the mechanism responsible for the origin of life. It also is a fact of life that all-to-commonly thwarts the technology we have developed to provide us with food and prevent and treat diseases. Bacterial, viral, fungal, and protozoan resistance to antimicrobial agents is a prime example of this downside of evolution's confrontation with public health and medical care and technology. Resistance has evolved to virtually every major infectious microbe and increasingly leads to failure of patient treatments that had been effective and of preventive strategies like use of prophylactic antimicrobials. How can we can prevent and/or limit the rate of ascent of resistance in treated patients, in open communities, in hospitals, in day care facilities and in nursing homes? The research of a number of members of the PBEE faculty addresses this question from a theoretical, experimental and/or applied perspective.

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Ecology of vector-borne & zoonotic diseases
Of the three most important infectious diseases world-wide (HIV, malaria, and TB), one emerged from a zoonotic reservoir and one is the dominant vector-borne disease affecting humans. The vast majority of emerging threats to human health from infectious diseases are primarily associated with vectors and zoonotic reservoirs. The faculty in our program study many of the most important diseases (e.g. malaria, Chagas disease, Lyme disease, rabies, dengue, hantavirus, Ebola, etc.) both in the laboratory and in the field. Foci of research range from uncovering the molecular basis of host specificity to the basic population ecology of vectors and zoonotic reservoir species.

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