Extended observer to estimate the spreading of contagious disease

This paper focuses on nonlinear observer design for the well-known susceptible, Exposed, Infected and Removed (SEIR) model endowed with a treatment function T. This later makes it a piecewise dynamical system (hybrid system). Assuming that we know the infected population, this paper uses the extended observer normal form to estimate the number of susceptible and exposed individuals of population under a contagious diseases.