Monte Carlo simulation of the transmission of measles: beyond the mass action principle.

We present a Monte Carlo simulation of the transmission of measles within a population sample during its growing and equilibrium states by introducing two different vaccination schedules of one and two doses. We study the effects of the contact rate per unit time xi as well as the initial conditions on the persistence of the disease. We found a weak effect of the initial conditions while the disease persists when xi lies in the range 1/L-10/L (L being the latent period). Further comparison with existing data, prediction of future epidemics and other estimations of the vaccination efficiency are provided. Finally, we compare our approach to the models using the mass action principle in the first and another epidemic region and found the incidence independent of the number of susceptibles after the epidemic peak while it strongly fluctuates in its growing region. This method can be easily applied to other human, animal, and plant diseases and includes more complicated parameters.