Fig. 1.

Model diagram for RSV and Influenza (INF). Individuals could be either Susceptible (S), Infected, (I), Protected (P) or Recovered (R) to either virus. Following infection, (which occurred at rate ${\lambda }_{RSV,i}$ and ${\lambda }_{INF,i}$), recovery occurred at a constant rate (${\gamma }_{RSV}$ and ${\gamma }_{INF}$), and the population entered the P state. Here they are immune to the virus they were infected by and protected to a varying extent ($\sigma$) against infection from the second virus. This protection waned at rate ρ, and the population entered the R compartment. In the R compartment the population was immune to the virus it was infected by, but not the other virus. We ran the model for one season and compartments I_RSV,iP_INF,i and I_RSV,iR_INF,I, were combined, and P_RSV,iI_INF,I and R_RSV,iI_INF,I were combined, because they are effectively identical. Parameters were: age susceptibility to RSV infection (${\tau }_i$), For clarity, age structure is given only by the subscript (i), for further details see supplement section 2.