Fig 2. The nested model structure for exploring age-prevalence data for RSV using catalytic infection models.

The compartments in the model represent the following states of the population: M = Individuals with maternally acquired antibodies (split into 2, M₁ and M₂ to allow for improved fit), S₀ = Seronegative after loss of maternally acquired antibodies, F₀ = Permanent seropositive status after infection, F₁ = Temporary seropositive status after primary infection, S₁ = Seronegative after loss of infection acquired antibodies. When p = 0, the model reduces to MSF, when p = 1 and only 1 rate of infection is estimated (λ₀ = λ₁) the model is MSFSF₁ and with p = 1 and 2 rates of infection estimated (λ₀ ≠ λ₁) the model is MSFSF₂.