Table 2.
Best fit initial conditions used in the YF model, fitted to the 2017/18 YF virus outbreak in Brazil (Ministry of Health, 2018).
| Symbol | Name | Value | Source |
|---|---|---|---|
| N | Total human population | 209,469,000 | United Nations Population Division (2019) |
| S | Susceptible humans | 41,893,754 | Total human population minus remaining human compartments (N – E − I – A – R) Approximately 20% of the population is estimated to be susceptible. |
| E | Exposed humans | 0 | Estimated |
| I | Infectious humans (symptomatic) | 21 | First day of case count |
| A | Infectious humans (asymptomatic) | 25 | Estimated from proportion of symptomatic humans |
| R | Recovered | 0.8∗N | Estimated, where about 50–60% of the overall population show immunization records (Shearer et al., 2017) and 97% of a rural Brazilian population show titres to YF virus (Machado et al., 2013) |
| D | Total human deaths due to YF | 0 | Estimated |
| M | Total mosquito population | 418,938,000 | Estimated double human population (Fitzgibbon et al., 2017; Wang et al., 2017) |
| X | Susceptible mosquitoes | 418,937,761 | Total mosquito population minus remaining mosquito components (M – Y – Z) |
| Y | Exposed mosquitoes | 150 | Fitted to the 2017/18 YF virus outbreak in Brazil (Ministry of Health, 2018) |
| Z | Infectious mosquitoes | 995 | Fitted to the 2017/18 YF virus outbreak in Brazil (Ministry of Health, 2018) |