Statistics of infections with diversity in the pathogenicity
  The statistics of outbreaks in a model for the propagation of meningococcal diseases is analyzed, taking into account the possibility that the population is fragmented into weakly connected patches. It is shown that, depending on the size of of the sample studied, the ratio between the variance and the mean of infected cases can vary from one (Poisson statistics) to the inverse of the infection rate. 
F. Guinea, V. A. A. Jansen, N. Stollenwerk