IMMUNITY BOOSTED BY LOW-LEVEL OF EXPOSURE TO INFECTION IN AN SIRS MODEL

The development of immunity in the susceptible class by a continuous l ow level of infection is a commonly observed phenomenon in many infect ious diseases. This important feature has been incorporated in an SIRS epidemiological model with both the rates of incidence and increase o f immunity being nonlinear in nature, instead of being bilinear, of th e form beta(1)I(p)S and beta(2)I(p)'S (0<p'<p, p not equal and p not e qual 1) respectively. The local and global behaviour of the dynamics o f the model have been investigated.