The epidemic began in Guinea during December 2013, 2 and the World Health Organization (WHO) was officially notified of the rapidly evolving EVD outbreak on March 23, 2014. There are numerous reports of symptomatic persons evading diagnosis and treatment, of laboratory diagnoses that have not been included in national databases, and of persons with suspected EVD who were buried without a diagnosis having been made. The true numbers of cases and deaths are certainly higher. In terms of reported morbidity and mortality, the current epidemic of EVD is far larger than all previous epidemics combined. Assuming no change in the control measures for this epidemic, by November 2, 2014, the cumulative reported numbers of confirmed and probable cases are predicted to be 5740 in Guinea, 9890 in Liberia, and 5000 in Sierra Leone, exceeding 20,000 in total.ĪS OF SEPTEMBER 14, 2014, A TOTAL OF 4507 confirmed and probable cases of Ebola virus disease (EVD), as well as 2296 deaths from the virus, had been reported from five countries in West Africa - Guinea, Liberia, Nigeria, Senegal, and Sierra Leone.
On the basis of the initial periods of exponential growth, the estimated basic reproduction numbers ( R 0) are 1.71 (95% CI, 1.44 to 2.01) for Guinea, 1.83 (95% CI, 1.72 to 1.94) for Liberia, and 2.02 (95% CI, 1.79 to 2.26) for Sierra Leone. The course of infection, including signs and symptoms, incubation period (11.4 days), and serial interval (15.3 days), is similar to that reported in previous outbreaks of EVD. The majority of patients are 15 to 44 years of age (49.9% male), and we estimate that the case fatality rate is 70.8% (95% confidence interval, 69 to 73) among persons with known clinical outcome of infection.