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Transmission Bottlenecks as Determinants of Virulence in Rapidly Evolving Pathogens
Carl T. Bergstrom, Paul McElhany and Leslie A. Real
Proceedings of the National Academy of Sciences of the United States of America
Vol. 96, No. 9 (Apr. 27, 1999), pp. 5095-5100
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/47354
Page Count: 6
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Transmission bottlenecks occur in pathogen populations when only a few individual pathogens are transmitted from one infected host to another in the initiation of a new infection. Transmission bottlenecks can dramatically affect the evolution of virulence in rapidly evolving pathogens such as RNA viruses. Characterizing pathogen diversity with the quasispecies concept, we use analytical and simulation methods to demonstrate that severe bottlenecks are likely to drive down the virulence of a pathogen because of stochastic loss of the most virulent pathotypes, through a process analogous to Muller's ratchet. We investigate in this process the roles of host population size, duration of within-host viral replication, and transmission bottleneck size. We argue that the patterns of accumulation of deleterious mutation may explain differing levels of virulence in vertically and horizontally transmitted diseases.
Proceedings of the National Academy of Sciences of the United States of America © 1999 National Academy of Sciences