The magnitude and pace of the current Ebola outbreak is unprecedented and requires tools to assess the future scope of the epidemic, as well as the efficacy of intervention tools and strategies. Unfortunately, our understanding of Ebola transmission dynamics is incomplete and data on the present outbreak are limited. Consequently, we present our forecasts as estimates, and cannot provide well-constrained certainties or likelihoods to any of the predicted outcomes.

Data: Ebola data for Guinea, Liberia, and Sierra Leone were compiled from the World Health Organization’s Disease Outbreak News. Total cases and deaths were used to train these model forecasts. The data include confirmed, probable, and suspected cases and may therefore decrease between measurements should some of the unconfirmed cases (i.e. the probable and suspected cases) be excluded after testing.

Methods: The model used to generate these forecasts contains a stochastic component that allows the force of transmission to vary through time. This variability is intended to emulate the spatial-temporal variability of Ebola transmission dynamics within country due to changes in intervention, containment and social practices. Three scenarios are forecast using the optimized model:

  1. an improved scenario, in which intervention and containment, as estimated during the assimilation process, are more effective in the future;
  2. a no change scenario, in which intervention and containment, as estimated during the assimilation process, continues with the same efficacy;
  3. a degraded scenario, in which intervention and containment, though not absent, are less effective in the future.
At present the no change scenario forecasts have best matched observed outcomes, indicating indicating continued exponential growth in all three countries and no substantial change in the efficacy of interventions in recent weeks. Guinea may be an exception: the 8/31/14 forecasts projected increased exponential growth; however, the most recent forecasts (9/7/14) project a less aggressive growth of the epidemic, in line with prior predictions (e.g. 8/24/14).

Mean estimates of cumulative cases of Infections (upper-pane) and Mortality (lower-pane) are shown below. The shaded region around the forecasts shows the interquartile range. A forecast horizon of 6 weeks is displayed. Hover on a data point to look at values. Use the Fit Cutoff slider at the top right to base estimates on a different observation cutoff date and Country selection box to see estimates for a different country. Use the Intervention selection box to see the forecasts under different scenarios.