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

p _i , q _i

effect of specific and cross reactive immune response on strain i

c _i , k _i

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.