Winter is coming: Pathogen emergence in seasonal environments
Fig 5
Probability of Zika emergence across space and time.
The top figures (A and B) show the seasonal variations in λIV, EH, the transmission rate from humans to the vectors because of the fluctuations the density of vectors in two habitats (this illustrates the effect of space on Zika emergence): a minor variation in mean temperature, 29°C (A and C) versus 27°C (B and D), has a massive impact on transmission and, consequently, on pathogen emergence. In C and D we illustrate the effect of the time of introduction t0 on Zika emergence. The dotted black line refers to the naive expectation for the probability of pathogen emergence at time t0 if all the rates were constant and frozen at their t0 values (see (7)). The gray shading in B and D refers to the low transmission season where the product of the transmission rates is lower than the product of death rates (see S1 Text). The exact probability of emergence pe(t0 T, T) is indicated as a solid black line. Higher seasonality (B and D) increases the discrepancy between the naive expectation and the exact value of the probability of pathogen emergence. This discrepancy is due to the winter is coming effect (light gray shading in D). Parameter values are given in table S1 A (model I) of section 3 of S1 Text.