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Biological Sciences


In most host-pathogen systems, the key feature of transmission dynamics and rate of spread of a parasite or disease is the variation among hosts in the numbers of parasites they harbor and the factors controlling infection. Pathogens are typically aggregated across their host populations: relatively few individuals are heavily infected, while most potential hosts suffer light infections or remain uninfected. Aggregation among hosts may be generated by variation among individuals in their exposure to parasite infective stages and by variation in susceptibility once an infectious agent has been encountered. Host heterogeneity in parasite burden has a strong influence on the establishment and subsequent spread of pathogens. Understanding the basis of this variation is critical to understanding transmission dynamics and the development of effective mitigation strategies.