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Two theorems on solutions of differential-difference equations and applications to epidemic theory

Published online by Cambridge University Press:  14 July 2016

Norman C. Severo*
Affiliation:
State University of New York at Buffalo

Extract

We present two theorems that provide simple iterative solutions of special systems of differential-difference equations. We show as examples of the theorems the simple stochastic epidemic (cf. Bailey, 1957, p. 39, and Bailey, 1963) and the general stochastic epidemic (cf. Bailey, 1957; Gani, 1965; and Siskind, 1965), in each of which we let the initial distribution of the number of uninfected susceptibles and the number of infectives be arbitrary but assume the total population size bounded. In all of the references cited above the methods of solution involve solving a corresponding partial differential equation, whereas we deal directly with the original system of ordinary differential-difference equations. Furthermore in the cited references the authors begin at time t = 0 with a population having a fixed number of uninfected susceptibles and a fixed number of infectives. For the simple stochastic epidemic with arbitrary initial distribution we provide solutions not obtainable by the results given by Bailey (1957 or 1963). For the general stochastic epidemic, if we use the results of Gani or Siskind, then the solution of the problem having an arbitrary initial distribution would involve additional steps that would sum proportionally-weighted conditional results.

Type
Research Papers
Copyright
Copyright © Sheffield: Applied Probability Trust 

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References

Bailey, N. T. J. (1957). The Mathematical Theory of Epidemics. London: Charles Griffin and Co. Ltd.Google Scholar
Bailey, N. T. J. (1963). The simple stochastic epidemic: a complete solution in terms of known functions. Biometrika, 50, 235240.Google Scholar
Gani, J. (1965). On a partial differential equation of epidemic theory. I. Biometrika, 52, 617622.Google Scholar
Siskind, V. (1965). A solution of the general stochastic epidemic. Biometrika, 52, 613616.CrossRefGoogle ScholarPubMed