Table 2.
Modelled estimates of Ebola virus exportation from Guinea, Liberia, and Sierra Leone via commercial air travel
| Population estimates* | Number of active cases† | Estimated prevalence (per 100 000) | Number of monthly international travellers (outbound, unrestricted air travel)‡ | Projected number of infected travellers per month (outbound, unrestricted air travel)§ | Projected time to one internationally exported case (unrestricted air travel) | Projected time to one internationally exported case (restricted air travel)¶ | |
|---|---|---|---|---|---|---|---|
| Guinea | 11 745 189 | 292 | 2·49 | 14 732 | 0·37 | 2·7 months | 8·0 months |
| Liberia | 4 294 077 | 1707 | 39·75 | 12 781 | 5·08 | 0·2 months | 0·4 months |
| Sierra Leone | 6 092 075 | 737 | 12·10 | 14 237 | 1·72 | 0·6 months | 3·9 months |
| Total | 22 131 341 | 2736 | 18·11 (19·3)** | 41 750 | 7·17 | 0·14 months | 0·35 months |
Source: World Bank, 2013.
Sum of the number of confirmed, probable, and suspected cases in the past 21 days to estimate active cases as of Sept 21, 2014.
Based on average traveller volumes recorded between Sept 1, 2013, to Dec 31, 2013; includes international travel between Guinea, Liberia, and Sierra Leone.
Model assumptions include: Ebola virus disease activity is constant and equally distributed across the population; an individual's risk of Ebola virus infection is independent of the probability of international air travel; we calculated projected numbers of internationally outbound travellers infected with Ebola virus using the following formula: [number of active cases/country population] × monthly number of international outbound air travellers); we calculated the time to one internationally exported case as the inverse of the projected number of Ebola virus exportations per month (using case counts as of Sept 21, 2014).
We assumed a reduction in international air travel volume of 51% for Liberia, 66% for Guinea, and 85% for Sierra Leone.
Represent mean value (SD) for the three countries.