Table 1.

Variables and parameters in equations (1)

v i	viral load from strain i
x i	specific immune response to strain i
z	cross reactive immune response
r i	growth rate of virus i
pi, qi	effect of specific and cross reactive immune response on strain i
ci, ki	growth of specific and cross reactive immune response induced by and directed against strain i
b	natural decay of the immune response
u i	decay of immune response induced by strain i.