THE OUTCOME OF A STOCHASTIC EPIDEMIC—A NOTE ON BAILEY'S PAPER

Peter Whittle

Biometrika · 1955 · 257 citations · 4 references

Concepts

TL;DR

Bailey (1953) extended Bartlett’s stochastic epidemic model, showing that the distribution of the final epidemic size can be obtained by solving doubly recurrent relations. The author aims to demonstrate that, in general, these probabilities can be derived via singly recurrent relations. This is achieved by solving the singly recurrent relations (eqs. 17 and 24) and deriving expressions (eqs. 38 and 40) for the take‑off probability, providing a stochastic analogue of the Kermack–McKendrick threshold.

Abstract

In a recent paper (1953) N. Bailey has considered a stochastic epidemic model of the type set up by Bartlett (1949), and has shown that the probability distribution (Pw) of the ultimate number of infected individuals (w) may be calculated by solving a certain set of doubly recurrent relations. I propose to show that for quite a general case these same probabilities may be obtained by the solution of a set of singly recurrent relations (eqs. (17) and (24)). Furthermore, an expression may be derived (eqs. (38) and (40)) for the probability that an infection introduced into a large population will 'take'—this provides a stochastic equivalent to Kermack & McKendrick's threshold theorem (1927 and later).

References

4