Ebola Fatality Rate 74% in Sierra Leone; Bleeding Is Rare

Laurie Barclay, MD

October 30, 2014

Among 106 patients diagnosed with Ebola virus disease (EVD) in Sierra Leone, the incubation period was 6 to 12 days, the case fatality rate was 74%, and only one patient had bleeding, according to a retrospective case series published online October 29 in the New England Journal of Medicine.

"In past outbreaks, EVD has been characterized by a constellation of signs and symptoms beginning with fever and progressing to diarrhea, vomiting, and, in a subgroup of patients, hemorrhage," write John Schieffelin, MD, from the Department of Medicine and the Department of Pediatrics, Tulane University School of Medicine, New Orleans, Louisiana, and colleagues. "However, the sporadic nature of [Ebola virus] outbreaks and their occurrence in remote, resource-limited settings have precluded the acquisition of extensive clinical and laboratory data."

Since the beginning of the EBV outbreak in Sierra Leone, the Kenema Government hospital there has admitted and treated patients with EVD. The preexisting capability of that facility for research on viral hemorrhagic fever allowed the collection of clinical and laboratory data on patients with EVD.

Between May 25 and June 18, 2014, there were 106 patients diagnosed with EVD, of whom 87 had a known outcome and 44 had availability of detailed clinical data. Frequent presenting symptoms were fever (89%), headache (80%), weakness (66%), dizziness (60%), diarrhea (51%), abdominal pain (40%), and vomiting (34%). Bleeding occurred in only one patient.

The estimated incubation period was 6 to 12 days, and the overall case fatality rate was 74%. Presenting features associated with mortality were fever, weakness, dizziness, diarrhea, and older age, as well as elevated blood urea nitrogen, aspartate aminotransferase, creatinine, and high Ebola virus load.

Consistently higher aspartate aminotransferase than alanine aminotransferase values suggest that tissue damage, including rhabdomyolysis, may play a role in EVD.

Compared with patients older than 45 years, those younger than 21 years had a lower case fatality rate (57% vs 94%; P = .03), according to exploratory analyses.

Quantitative reverse transcriptase-polymerase chain reaction assays to determine Ebola virus load in a subgroup of patients showed that case fatality rate was lower in patients presenting with fewer than 100,000 Ebola virus copies/mL (33%) than in those presenting with 100,000 or more Ebola virus copies/mL (94%; P = .003).

"The incubation period and case fatality rate among patients with EVD in Sierra Leone are similar to those observed elsewhere in the 2014 outbreak and in previous outbreaks," the authors write. "Although bleeding was an infrequent finding, diarrhea and other gastrointestinal manifestations were common."

This research was supported by the National Institutes of Health, the National Science Foundation, and the World Bank.

N Engl J Med. Published online October 29, 2014. Full text

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