A meta-analysis of previous Ebola outbreaks from the Democratic Republic of the Congo (DRC)—the epicenter of the current African outbreak—finds a high but improving mortality rate and identifies hemorrhage as a key predictor of death, although the certainty of evidence varied widely.
The University of Kinshasa researchers say the findings of the meta-analysis, published today in BMC Infectious Diseases, underscore the importance of early access to care, high-quality supportive management, and sustained implementation of effective therapeutic strategies to further lower the Ebola-related death rate, especially in areas with scarce resources.
The meta-analysis included 10 observational studies and one randomized controlled trial on Ebola death rates published up to November 10, 2025.
The study was conducted to update and fill gaps in the literature, the study authors said. “Available studies are heterogeneous with respect to diagnostic criteria, definitions of mortality, therapeutic strategies, and the quality of supportive care,” they wrote. “In addition, results are often derived from single-center cohorts with limited sample sizes, substantial loss to follow-up, and insufficient adjustment for confounding factors.”
It’s important to note that the current DRC outbreak, which totaled 600 suspected cases and 139 deaths as of this morning, is caused by the Bundibugyo Ebola strain, which has been identified in only two previous outbreaks, in 2007 and 2012, and was not the causative strain in the studies included in this analysis. Bundibugyo is of particular concern because no vaccines or treatments for it have been approved.
Death rate higher in early epidemic
The 11 included studies were published from 2015 to 2025 and covered epidemics ranging from 2013 to 2020. Most studies were conducted in West African countries, mainly Guinea, Sierra Leone, and Liberia, while two studies were from the DRC. There was no statistically detectable publication bias.
Sample sizes ranged widely, from 61 to 14,163 participants, with a mean or median age of 3 to 39 years, reflecting both pediatric and adult populations.
Available studies are heterogeneous with respect to diagnostic criteria, definitions of mortality, therapeutic strategies, and the quality of supportive care.
Case-fatality rates among 16,413 Ebola patients ranged from 34% to 79%, with a pooled mortality rate of 54% among hospitalized patients, but the certainty of evidence for this finding was deemed low because of high inter-study heterogeneity and the observational nature of most included studies. The 95% prediction interval ranged from 20.3% to 87.6%, indicating wide variability in death rates by setting.
The mortality rate was higher (56%) during the 2014-16 West African epidemic—the largest Ebola outbreak thus far—than in the 2018-20 Central African outbreaks (43%). The higher mortality rate in the earlier outbreak was likely due to the extreme strain on healthcare systems, delays in case detection, and major logistical problems at that time.
The Central African outbreaks had lower and more homogeneous mortality (43%), likely reflecting improvements in care organization, the introduction of standardized supportive care protocols, and access to new therapies such as monoclonal antibodies, the researchers said.
Pediatric mortality (46%) appeared lower than that of adults (56%), but the small number of pediatric studies and widely overlapping confidence intervals didn’t support a definite conclusion.
Among the clinical risk factors for death, hemorrhagic manifestations were most strongly linked (odds ratio [OR], 3.52), with a moderate certainty of evidence owing to the consistent direction of effect and a relatively large pooled effect estimate. Diarrhea may also be a risk factor, although the certainty of evidence was rated as very low because of serious imprecision, inconsistency, and the limited number of studies (OR, 6.64).
While age didn’t appear associated with risk of death, the substantial heterogeneity across studies limited the ability to interpret this finding.
Sensitivity analyses that excluded studies at higher risk of bias and considered the influence of large studies didn’t substantially change the estimated pooled death rate.
Still one of the most deadly human infections
The findings confirm that Ebola remains one of the most deadly human infections, consistent with case-fatality rates reported in previous outbreaks of 25% to 90%, depending on the virus strain and healthcare context. “These findings are also consistent with comprehensive reviews describing persistently high EVD [Ebola virus disease] mortality despite advances in clinical management,” the authors wrote.
These findings are also consistent with comprehensive reviews describing persistently high EVD [Ebola virus disease] mortality despite advances in clinical management.
They recommended strengthening surveillance systems, healthcare infrastructure, and rapid access to Ebola treatment centers and therapies and implementing evidence-based clinical protocols to improve survival.
The findings, however, should be interpreted with caution because the pooled effect estimates were derived from unadjusted ORs in the observational studies, the researchers noted.
“The considerable heterogeneity between studies likely stems primarily from major contextual differences between Ebola outbreaks in access to treatment, case management, viral loads at hospital admission, and healthcare facility strain,” they wrote. “These limitations highlight the need for standardized data collection, improved reporting of key clinical variables, and more rigorous study designs in future outbreaks.”
