DOI: 10.17037/data.41
title: Asymptomatic infection and family contact patterns in households of Ebola Virus Disease survivors, Sierra Leone 2015

description: The data set contains information on 937 people (living and dead) who were resident in the households of people who survived Ebola Virus Disease (EVD) in the Kerry Town Ebola Treatment Centre in Western Area Province, Sierra Leone, during the 2014-2016 epidemic. It includes individual and household characteristics, information on exposure levels, symptoms experienced by individuals during the period when the household was affected by EVD, outcomes, possible routes of transmission, and ELISA results from antibody testing for Ebola IgG in oral fluid. Survivor households were chosen because they were more easily contactable through the Save the Children survivors outreach programme: 123 of 152 survivors and their households were interviewed.
description: The study used qualitative interview methods to obtain quantitative data. All survivors discharged from Kerry Town Ebola Treatment Centre (ETC), Sierra Leone between November 2014 and March 2015 and living in the Western Area (or their parents/guardians) were contacted by the study team during July-August 2015 and invited to bring all household members who were present at the time Ebola was affecting their household to an interview. Households were defined as people eating from the same ‘pot’ at the time Ebola was in the household, regardless of the time they had spent in the household, and including people who joined the household during the Ebola period. 

Each household was interviewed separately. Individual written informed consent was requested from all members, with parents/guardians providing consent for those under 18 years. At the interview we first drew up an inventory of all household members, noting their age, sex, and whether or not they had had or had died of Ebola virus disease. A member of the study team then demonstrated the oral swab and self-administered oral swabs were collected from all consenting participants (with parents helping young children). These were stored at -20◦C for later testing for Ebola IgG in the Immunology and Applied Biotechnology Research Laboratory of University of Makeni, Sierra Leone, in January 2016. As a group, household members were then asked to describe what had happened in the household in their own words. For each person reported by the family as having had Ebola we asked about symptoms while at home, who had helped them while they were ill, shared a bed or had other contact with them, and who had contact with their body if they died. Adults spoke for young children and corroborated information from older children. In this way, using probing questions, we assigned a maximum exposure for each household member using predefined levels, which we had developed based on the literature and discussion with staff from the Ebola Treatment Centre. (see Additional Information section below for detail of exposure measurement).
We also asked about exposures outside the home and classified them on the same scale. For those not reported to have had Ebola we asked about symptoms at the time others in the household had Ebola. EVD cases were defined as laboratory-confirmed survivors and deaths from Kerry Town or other ETCs, and all those whom the family reported as having died of Ebola. Deaths for which the family was unsure of the cause, and, for some analyses, symptomatic individuals who were not tested or diagnosed with Ebola at the time, were classified as probable EVD if they fitted the Sierra Leone case definition of probable cases. The most likely primary or co-primary cases were identified for each household, and order of illness among other cases recorded if mentioned. To avoid overburdening participants, we did not collect time sequences or dates. We also did not directly ask family members who they thought transmitted to whom to avoid stimulating blame or ill-feeling among already traumatised families. 

All interviews were done in the participants’ language by multi-lingual study teams, and key outcomes were recorded in English on household inventory and individual forms. During the interview, one team member was the focal point, maintaining eye contact with the participants and guiding the discussion. A minimum of two other study team members listened and made notes, asking questions only if an issue was overlooked. This avoided multiple conversations taking place at the same time as well as ‘tick-box’ questioning. Study members were trained extensively so as not to need to use a paper interview guide to avoid loss of connection with the family group. Immediately after the family departed, the team sat together to discuss the story to make sure all elements were understood and data, including each person’s maximum level of exposure, were finalised.

Oral fluid samples were tested for Ebola virus glycoprotein IgG using an IgG Capture assay based on the EBOV Mayinga GP antigen (rGPδTM, IBT Bioservices Inc. USA cat.0501-016). Two positive controls and four negative controls were included in each plate. The cut-off for a reactive result was defined per plate as the mean optical density (OD) of the negative controls plus a fixed OD measure (0.1). Data are given as “normalised ODs”, i.e. the ratio of the test OD to the cut-off, so results &gt;1 are reactive. Tests were repeated for positive samples and some negative samples, including those with unexpected results and samples nearer the cut-off.