Time Evolution of Non-Lethal Infectious Diseases: A Semi-Continuous   Approach
  A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza. 
A. Noviello, F. Romeo and R. De Luca