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Stochasticity generates an evolutionary instability for infectious disease
Author(s) -
Read Jonathan M.,
Keeling Matt J.
Publication year - 2007
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1111/j.1461-0248.2007.01078.x
Subject(s) - instability , ecology , infectious disease (medical specialty) , biology , evolutionary biology , disease , physics , medicine , mechanics , pathology
Traditional models of disease evolution are based upon the deterministic competition between strains that confer complete cross‐immunity, and predict the selection of strains with higher basic reproductive ratios ( R 0 ). In contrast, evolution in a stochastic setting is determined by a complex mixture of influences. Here, to isolate the impact of stochasticity, we constrain all competing strains to have an equal basic reproductive ratio – thereby eliminating deterministic selection. The resulting stochastic models predict an evolutionary unstable strategy, which separates a region favouring the evolution of rapid‐transmission (acute) strains from one favouring persistent (chronic) strains. We find this to be a generic phenomenon with strain evolution consistently driven towards extremes of epidemiological behaviour. Even in the absence of an equal R 0 constraint, such stochastic selective pressures operate in addition to standard deterministic selection and will therefore influence the evolutionary behaviour of disease in all scenarios.