MICROPARASITE POPULATION-DYNAMICS AND CONTINUOUS IMMUNITY

A mathematical model is presented for the transmission of a microparas ite where the hosts occupy one of two states, uninfected or infected. In each state, the hosts are distributed over a continuous range of im munity. The immune levels vary within hosts due to the processes of wa ning of immunity (when uninfected), and increasing immunity (when infe cted), eventually resulting in recovery. Immunity level also influence s the host's ability to infect or be infected. Thus the proposed model incorporates both inter- and intra-host dynamics. It is shown from eq uilibrium results that this model is a general form of the susceptible -infected-resistant (SIR) and susceptible-infected-susceptible (SIS) f amily of models, a development that is useful for exploring multistrai n pathogen transmission and use of vaccines which confer temporary pro tection.