Exposure Patterns Driving Ebola Transmission in West Africa: A Retrospective Observational Study

Agua-Agum, Junerlyn; Ariyarajah, Archchun; Aylward, Bruce; Bawo, Luke; Bilivogui, Pepe; Blake, Isobel M.; Brennan, Richard J.; Cawthorne, Amy; Cleary, Eilish; Clement, Peter; Conteh, Roland; Cori, Anne; Dafae, Foday; Dahl, Benjamin; Dangou, Jean-Marie; Diallo, Boubacar; Donnelly, Christl A.; Dorigatti, Ilaria; Dye, Christopher; Eckmanns, Tim; Fallah, Mosoka; Ferguson, Neil M.; Fiebig, Lena; Fraser, Christophe; Garske, Tini; Gonzalez, Lice; Hamblion, Esther; Hamid, Nuha; Hersey, Sara; Hinsley, Wes; Jambei, Amara; Jombart, Thibaut; Kargbo, David; Keita, Sakoba; Kinzer, Michael; George, Fred Kuti; Godefroy, Beatrice; Gutierrez, Giovanna; Kannangarage, Niluka; Mills, Harriet L.; Moller, Thomas; Meijers, Sascha; Mohamed, Yasmine; Morgan, Oliver; Nedjati-Gilani, Gemma; Newton, Emily; Nouvellet, Pierre; Nyenswah, Tolbert; Perea, William; Perkins, Devin; Riley, Steven; Rodier, Guenael; Rondy, Marc; Sagrado, Maria; Savulescu, Camelia; Schafer, Ilana J.; Schumacher, Dirk; Seyler, Thomas; Shah, Anita; Van Kerkhove, Maria D.; Wesseh, C. Samford; Yoti, Zabulon

Our analyses provide a quantitative basis for prevention measures against the spread of Ebola, but also highlight the challenges faced in the field. A compassionate response protocol needs to acknowledge that, as we found, most reported potential transmissions occurred between family members close to the time of death of the case. This provides evidence that ring vaccination methods, such as those trialled in Guinea [45] , may be an effective way of delivering vaccines against Ebola in the context of limited supply or in hard-to-reach populations. Hospitalisation was found to be protective, but left substantial room for improvement. The association between reported funeral attendance and district-level epidemic trends highlights the continued need for improving access to and acceptability of safe burials of Ebola cases. More robust associations could be detected using case-control studies, but these are hard to coordinate during an emergency situation. In their absence, the analyses reported here have already provided key insights into the drivers of the epidemic. Heterogeneities in transmission made the road to Ebola elimination likely to be marked by episodic flare-ups [46, 47] . Ebola is controllable using the simple measures that have already been implemented in this outbreak, but complacency as case numbers decline could prolong the epidemic for months. Continued real-time data capture, reporting, and analysis are vital to track transmission patterns, inform resource deployment, and thus hasten elimination of the virus from the human population.