Duration of Immunity to Norovirus Gastroenteritis
Figure 1. . . Model schematic illustrating the immunity and infection states of the population with respect to norovirus (NoV) infection and the flows between those states. Persons are born directly into the susceptible pool, become exposed at the force of infection, and then progress through symptomatic and asymptomatic stages before arriving in the recovered compartment, which represents immunity to disease, but not necessarily to infection. As such, from the recovered compartment, persons can become asymptomatically infected at the force of infection or can become susceptible to disease once again through the waning of immunity. For the sake of simplicity, deaths from all categories equal to the incoming births are not shown but are included in the model code. In 1 iteration of the model (scenario E), a compartment is included that represents a class of persons who are born with genetic resistance (in gray to represent absence in all other model iterations) to NoV infection.