© 1972 by Biometrika Trust
On Downton's carrier-borne epidemic
University of Sheffield
The stochastic version of Downton's (1968) carrier-borne epidemic is considered. From the time-dependent solution, obtained by Gani's (1967) technique, the distribution of the total size of the continuous time epidemic is found, in a form suitable for computer calculations. Two additional results obtained seem useful and practical. An (n + 1) x (n + 1) matrix with first column the distribution of the size of an epidemic initiated by n susceptibles and a. carriers is shown to give the distributions of epidemics initiated by 0, ..., n 1 susceptibles and a carriers; this matrix is also shown to be the
-fold product of a similar matrix for epidemics initiated by just one carrier. The first of the additional results has an analogue for the time-dependent solution.
Key Words: Carrier-borne epidemic Time-dependent distribution of the size of epidemic Distribution of total size of epidemic