Figure 1

Sojourn time distribution in the primary infection state. Exponential distribution for the time infected individuals remain in primary state (P), and proportional progression to active disease (I) and latent (L) states. The curves are given by P(t) = e ^{− δ ⋅ t}, I(t) = ϕ ⋅ (1 − e ^{− δ ⋅ t}), L(t) = (1 − ϕ) ⋅ (1 − e ^{− δ ⋅ t}), with parameter values ϕ = 0.05 and δ = 2 yrs⁻¹, in agreement with the expectation that 5% of primary cases progress to active disease within 2 years of infection (dotted-line).