[The first model of the epidemic process in the works of P. D. En'ko]

The contribution of P. D. En'ko into the development of theoretical basis of epidemiology is briefly characterized. The study under consideration was published in 1889. En'ko succeed in correlating a discrete time model with actual cases of a measles epidemic which he observed in closed educational institutions of St. Petersburg. His remarkable investigation anticipated by nearly 40 years the Reed-Frost model.