Mathematical modeling of the West Africa Ebola epidemic

Abstract

As of November 2015, the Ebola virus disease (EVD) epidemic that began in West Africa in late 2013 is waning. The human toll includes more than 28,000 EVD cases and 11,000 deaths in Guinea, Liberia, and Sierra Leone, the most heavily-affected countries. We reviewed 66 mathematical modeling studies of the EVD epidemic published in the peer-reviewed literature to assess the key uncertainties models addressed, data used for modeling, public sharing of data and results, and model performance. Based on the review, we suggest steps to improve the use of modeling in future public health emergencies.

Keywords: ebola; epidemiology; forecasting; global health; human; modeling.

Figure 1.. Literature search flow.

DOI: http://dx.doi.org/10.7554/eLife.09186.003

Figure 2.. Cumulative number of modeling applications by date of most recent EVD data used.

The figure includes 125 modeling applications across the 66 publications. DOI: http://dx.doi.org/10.7554/eLife.09186.005

Figure 3.. Publication lag by type of modeling application.

The vertical red and turquoise lines indicate the median lag for publications including and not including, respectively, the type of modeling application. DOI: http://dx.doi.org/10.7554/eLife.09186.006

Figure 4.. R₀ estimates by type of model input data.

Aggregate, case counts released by the WHO or Ministries of Health; Line-level, individual-level data from epidemiological investigations; Genomic, Ebola virus sequence data. The Figure excludes an outlier estimate of 8.33 for Sierra Leone (Fisman et al., 2014). DOI: http://dx.doi.org/10.7554/eLife.09186.007

Figure 5.. R₀ estimates and CIs by type of epidemiological input data.

Disaggregated data typically were weekly counts. Top row: Vertical lines indicate 95% CIs. Bottom row: Horizontal bars indicate median CI width. DOI: http://dx.doi.org/10.7554/eLife.09186.008

Figure 6.. R₀ estimates and CIs by model fitting method.

Top row: Vertical lines indicate 95% CIs. Bottom row: Horizontal bars indicate median CI width. DOI: http://dx.doi.org/10.7554/eLife.09186.009

Figure 7.. Accuracy of cumulative incidence forecasts.

Accuracy is shown as the ratio of predicted incidence to incidence subsequently reported by the WHO. 'Dampening' refers to various approaches to restrict the growth of forecasted incidence over time. Top row: Accuracy by date of forecast. Bottom row: Accuracy by forecast lead time ('Horizon'). The Figure excludes one forecast with horizon > 1 year (Fisman and Tuite, 2014). DOI: http://dx.doi.org/10.7554/eLife.09186.010