Table 1.

Variables used in equations.

Variable	Parameter
S	Susceptible
E	Exposed
I	Infected
R	Recovered
β	Probability of disease transmission per contact times the number of contacts per unit time
δ	Rate of progression from exposed to infectious or inverse of the incubation period
γ	Rate of progression from infected to recovered or the inverse of the generation time
N	Total population (S + E + I + R)