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

Early hospitalisation in facilities with the ability to isolate patients effectively-a key element of control efforts for Ebola-is clearly a priority to reduce community transmission. Investigations of the initial phase of this epidemic, as well as previous outbreaks, have highlighted the potential role of within-hospital transmission before or shortly after Ebola is identified as the causative agent [37, 38] . Here we found that hospitalisation, defined broadly as anything from visiting a clinic to admission to an ETU, reduced transmission risk, showing that prompt hospitalisation may be an effective intervention as long as appropriate control measures are applied. However, hospitalisation did not eliminate transmission risk, indicating that improvements in infection control are needed in many health care settings. It should be noted that the meaning of date of hospitalisation may be different among cases, depending on how many and which types of facilities they visited in the course of their disease, and furthermore that there is potential for misclassification in the recording or interpretation of information on hospitalisation. In particular, while the health care facility of first admission was commonly reported, patient transfers to other facilities may not have always been recorded. Thus, there may be ambiguity about the type of health care facility a case was in at a particular time. Such missing information reduces our ability to resolve differences between types of facilities in their effectiveness at implementing case isolation, which could lead to underestimation of differences between facility types in isolation effectiveness. However, our results are broadly consistent with analyses of the outbreak in Conakry [29] . Half of reported non-funeral exposures where the matched contact was eventually hospitalised occurred after the reported date of hospitalisation. These results underscore the importance of further improving infection control in all health care facilities, but particularly in non-ETUs. However, in contexts where hospital bed capacity is insufficient or infection control in health care settings is imperfect, greater consideration might be given to measures to reduce within-family exposure-for example, via education and/or providing a home protection kit with hand disinfectant, protective equipment, and clear guidance for those caring for sick family members.