OUTBREAK DYNAMICS: ACCURACY OF INITIAL OUTBREAK MAGNITUDE ESTIMATES
Since January 2015, significant progress has been made to contain the current Ebola outbreak. Multilateral efforts, supported by major global interests, are now producing results.[1] Although some may attribute the magnitude of the much-needed Ebola coordinated global response to the early Centers for Disease Control (CDC) modeling team estimates of as many as 1,400,000 possible infections in West Africa, others point out that this number overestimated the actual magnitude of the outbreak by approximately 65 times.[4] The CDC team responded that their estimates were made using a number of assumptions and represented the “worst case” scenario, which fortunately never materialized.[4]
Latest estimates from the World Health Organization (WHO) indicate that over 11,000 lives were lost to the deadly virus since the first documented case was officially recorded [Figure 1]. While there are still a few new cases and deaths, the outbreak appears to be progressing toward eradication. Figure 2 represents declining monthly mortality since the initial case reports in March of 2014. This trend is likely a reflection of more aggressive disease surveillance, early identification and clinical intervention, as well as the increased level of resources available as a result of international relief efforts. Additional age-stratified epidemiologic data for the current outbreak, including incubation period, onset of hospitalization, and onset of death are summarized in Figure 3.[5]
Figure 1  Total cases (red line) versus total deaths (black line) as reported by the World Health Organization between March 22, 2014 and August 19, 2015 (data reported for Guinea, Liberia, and Sierra Leone)
Figure 2  Five-period moving average of case fatality rate of Ebola (red line) as derived from the World Health Organization data between March 22, 2014 and August 19, 2015 (data from Guinea, Liberia, and Sierra Leone)
Figure 3  Age-stratified comparison of incubation periods, onset of death, and onset of hospitalization (expressed in days) for the current Ebola epidemic[5]