The spread of epidemics

摘要

The progress of an infection is studied as a function of time along the lines of Bailey's theory. However, the system of differential equations is solved without the assumption that the numbers of the susceptibles and the infectives remain constant. Assuming that the infectives remain infective forever—this is the case for some viral diseases—but do not necessarily fall ill, the model says that a part of the population will survive if the expectation for a susceptible to become an infective is less than the expectation for the infective to die during a certain time period Δt. The model further implies that the population will partly survive if it succeeds in adjusting the parameters governing the infectiousness of the disease as mentioned above before the infected part is too large.