Ebola virus disease in West Africa--the first 9 months of the epidemic and forward projections.

Abstract (PubMed)

BACKGROUND: On March 23, 2014, the World Health Organization (WHO) was notified of an outbreak of Ebola virus disease (EVD) in Guinea. On August 8, the WHO declared the epidemic to be a 'public health emergency of international concern.' METHODS: By September 14, 2014, a total of 4507 probable and confirmed cases, including 2296 deaths from EVD (Zaire species) had been reported from five countries in West Africa--Guinea, Liberia, Nigeria, Senegal, and Sierra Leone. We analyzed a detailed subset of data on 3343 confirmed and 667 probable Ebola cases collected in Guinea, Liberia, Nigeria, and Sierra Leone. RESULTS: The overall case fatality rate was 70.8% (95% confidence interval [CI], 69 to 73) among cases for which the outcome was known. Among the 3343 confirmed cases with known age and sex, 55.3% were female. Among all confirmed cases, 18.3% were health care workers. The mean (plus or minus SD) incubation period was 11.4 plus or minus 8.1 days; the mean serial interval was 15.3 days. The reproduction number at the start of the epidemic was 1.71 (95% CI, 1.44 to 2.01) in Guinea, 1.83 (95% CI, 1.72 to 1.94) in Liberia, and 2.02 (95% CI, 1.79 to 2.26) in Sierra Leone. CONCLUSIONS: Without drastic improvements in control measures, the numbers of cases of and deaths from EVD are expected to continue increasing from hundreds to thousands per week in the coming months.