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The devastating Ebola virus disease epidemic in West Africa continues to escalate. Although the task has been quite difficult, the WHO has been able to collect clinical and epidemiologic data for the first 9 months of the outbreak.
The epidemic likely began in December 2013 in Guinea (NEJM JW Infect Dis Sep 23 2014). As of September 14, 2014, the WHO had received reports of 4507 cases of Ebola virus disease (3075 confirmed, 1432 probable) with 2296 deaths. Detailed data were available for 4010 of these cases (3343 confirmed, 667 probable) from four countries — Guinea, Liberia, Nigeria, and Sierra Leone.
Case patients had a median age of 32 years; 62% were aged 15 to 44. The mean incubation period was 11.4 days. Fever was the most common (88%) manifestation. Specific hemorrhagic symptoms were reported in <1% to 6% of cases, but unexplained bleeding was reported in 20%. Among the 1737 cases with definitive recorded clinical outcomes, the case fatality rate was 71% (95% confidence interval, 69–73).
Based on the current rate of increase in Guinea, Liberia, and Sierra Leone — and assuming no change in control measures — the authors estimated that the total number of confirmed and probable cases in these countries would exceed 20,000 by early November 2014.
WHO Ebola Response Team.Ebola virus disease in West Africa — the first 9 months of the epidemic and forward projections. N Engl J Med 2014 Sep 23; [e-pub ahead of print]. (http://dx.doi.org/10.1056/NEJMoa1411100)
Farrar JJ and Piot P.The Ebola emergency — immediate action, ongoing strategy. N Engl J Med 2014 Sep 23; [e-pub ahead of print]. (http://dx.doi.org/10.1056/NEJMe1411471)
Comment
Contrary to what might be expected from the enormity of this epidemic, there have been no epidemiologic, clinical, or virologic features to suggest that the underlying virus is more virulent than those responsible for previous outbreaks. As noted by editorialists, the course of this worst-ever outbreak results from a combination of factors, including local customs, lack of trust in authorities after years of armed conflict, multiple deficiencies in disease control, and international indifference.