London School of Hygiene & Tropical Medicine

The DRC has experienced more Ebola outbreaks than any other country since the virus was discovered in 1976. The findings, published in eLife, combine epidemiological information and patient outcomes from all those outbreaks to provide insights into the mortality patterns of Ebola virus disease and describes the national and international interventions carried out during each outbreak.

The study was conducted by researchers from the London School of Hygiene & Tropical Medicine, UCL, Public Health England, the DRC Ministry of Public Health, and the Institut National de Recherche Biomédicale in the DRC.  

For the first time, the researchers have combined data from almost 1,000 Ebola cases reported over 38 years across the country.

The data suggests that rapidly-progressing outbreaks, where a sick person is likely to transfer the disease to at least three other people, are swiftly brought under control. Yet, during the slower-paced epidemics the national and international responses were slower and outbreaks were longer.

The study showed that nearly all the epidemics in the analysis were in decline before a national or international response, such as setting up isolation centres, was in place. The authors propose that behavioural changes in communities could be behind these early declines.

Study co-author Dr Marc Baguelin, Research Fellow at the London School of Hygiene & Tropical Medicine, said: "Less aggressive Ebola outbreaks that start slower are the ones most difficult to control. This is likely due to the delay in response and is typically what was observed in the devastating West Africa outbreak.

"We are making the precious historical data used in our study available to the scientific community to foster further work on understanding the transmission of the Ebola virus."

The researchers found that adults (individuals aged 25-64) are proportionately more likely to be affected by Ebola. This is similar to the experience during the West African outbreak, and could be explained by this section of the population being more likely to care for Ebola patients.

In outbreaks occurring in the DRC, children over the age of five and under 15 were consistently the least likely group to get sick or die from the virus. In contrast, contracting Ebola was fatal for all patients under the age of two.

The time between the onset of symptoms and admittance to hospital had a significant impact on the outcomes for the patients. Each day of delay before hospitalisation increased the risk of death by 11%. Delays in admittance to hospital could be influenced by many factors including geography, infrastructure and cultural influences.

This analysis could help target age groups for interventions such as vaccination if, for example, there is a shortage of supplies. It also highlights the importance of speed in future national and international responses to Ebola virus disease even if there are few cases. The researchers say dissemination of information about the disease, even in remote locations, is key. In addition, it shows the importance of rapid hospitalisation of future patients to their survival.

The dataset collated by the researchers allows for comparisons in trends between Ebola outbreaks in DRC and similar data gathered in other regions, to draw further lessons about the demographics, climate and political influences for the control of Ebola epidemics.

Publication

• Alicia Rosello, Mathias Mossoko, Stefan Flasche, Albert Jan Van Hoek, Placide Mbala, Anton Camacho, Sebastian Funk, Adam Kucharski, Benoit Kebela Ilunga, John Edmunds, Peter Piot, Marc Baguelin, Jean-Jacques Muyembe Tamfum. Ebola virus disease in the Democratic Republic of the Congo, 1976-2014. eLife. DOI: 10.7554/eLife.09015

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