Social Network Analysis of Ebola Virus Disease During the 2014 Outbreak in Sukudu, Sierra Leone.

Background: Transmission by unreported cases has been proposed as a reason for the 2013-2016 Ebola virus (EBOV) epidemic decline in West Africa, but studies that test this hypothesis are lacking. We examined a transmission chain within social networks in Sukudu village to assess spread and transmission burnout. Methods: Network data were collected in 2 phases: (1) serological and contact information from Ebola cases (n = 48, including unreported); and (2) interviews (n = 148), including Ebola survivors (n = 13), to identify key social interactions. Social links to the transmission chain were used to calculate cumulative incidence proportion as the number of EBOV-infected people in the network divided by total network size. Results: The sample included 148 participants and 1522 contacts, comprising 10 social networks: 3 had strong links (>50% of cases) to the transmission chain: household sharing (largely kinship), leisure time, and talking about important things (both largely non-kin). Overall cumulative incidence for these networks was 37 of 311 (12%). Unreported cases did not have higher network centrality than reported cases. Conclusions: Although this study did not find evidence that explained epidemic decline in Sukudu, it excluded potential reasons (eg, unreported cases, herd immunity) and identified 3 social interactions in EBOV transmission.

A post-outbreak assessment of exposure proximity and Ebola virus disease-related stigma among community members in Kono District, Sierra Leone: A cross-sectional study.

Background: Based on findings from other contexts, informed by intergroup contact theory, that more contact is associated with less stigma, we hypothesized that community members with greater exposure to cases of Ebola virus disease (EVD) were less likely to report EVD-related stigma towards EVD survivors. We assessed personal stigmatizing attitudes towards Ebola survivors, which reflects personal fear and judgement, as well as perceived stigma towards EVD survivors, which reflects an individual's perception of the attitudes of the community towards a stigmatized group. Methods: From September 2016 to July 2017, we conducted a cross-sectional, community-based study of EVD-related stigma among individuals who did not contract Ebola in four EVD-affected rural communities of Kono District, Sierra Leone. We identified individuals from all quarantined households and obtained a random sample of those who were unexposed. Exposed individuals either lived in a quarantined household or were reported to have been in contact with an EVD case. Our explanatory variable was proximity to an EVD case during the outbreak. Our primary outcome was stigma towards EVD survivors, measured by a 6-item adapted HIV-related stigma index validated in Zambia and South Africa, with 1 item reflecting personal stigmatizing attitudes and 5 items reflecting perceived community stigma. The 6-item EVD stigma index had good internal consistency (Cronbach's alpha=0.82). We used modified Poisson and negative binomial regression models, adjusting for potential confounders, to estimate the association between exposure proximity and EVD stigma. Results: We interviewed 538 participants aged 12 to 85 years. Most (57%) had been quarantined. Over one-third (39%) reported personal stigmatizing attitudes or perceived community stigma; the most frequently endorsed item was fear and judgment towards EVD survivors. Having contact with someone with EVD was significantly associated with a lower likelihood of perceived community stigma (prevalence ratio [PR], 0.26; 95% CI, 0.13-0.54) and personal stigmatizing attitudes (PR, 0.44; 95% CI, 0.29-0.65). In contrast, being quarantined was significantly associated with a higher likelihood of perceived community stigma (PR, 3.9; 95% CI, 1.5-10.1). Conclusions: In this cross-sectional study, we found evidence of an inverse relationship between EVD-related stigma and contact with an EVD case. This finding substantiates intergroup contact theory and may form the basis for anti-stigma interventions.

Association of Lower Exposure Risk With Paucisymptomatic/Asymptomatic Infection, Less Severe Disease, and Unrecognized Ebola Virus Disease: A Seroepidemiological Study.

Background: It remains unclear if there is a dose-dependent relationship between exposure risk to Ebola virus (EBOV) and severity of illness. Methods: From September 2016 to July 2017, we conducted a cross-sectional, community-based study of Ebola virus disease (EVD) cases and household contacts of several transmission chains in Kono District, Sierra Leone. We analyzed 154 quarantined households, comprising both reported EVD cases and their close contacts. We used epidemiological surveys and blood samples to define severity of illness as no infection, pauci-/asymptomatic infection, unrecognized EVD, reported EVD cases who survived, or reported EVD decedents. We determine seropositivity with the Filovirus Animal Nonclinical Group EBOV glycoprotein immunoglobulin G antibody test. We defined levels of exposure risk from 8 questions and considered contact with body fluid as maximum exposure risk. Results: Our analysis included 76 reported EVD cases (both decedents and survivors) and 421 close contacts. Among these contacts, 40 were seropositive (22 paucisymptomatic and 18 unrecognized EVD), accounting for 34% of the total 116 EBOV infections. Higher exposure risks were associated with having had EBOV infection (maximum risk: adjusted odds ratio [AOR], 12.1 [95% confidence interval {CI}, 5.8-25.4; trend test: P < .001) and more severe illness (maximum risk: AOR, 25.2 [95% CI, 6.2-102.4]; trend test: P < .001). Conclusions: This community-based study of EVD cases and contacts provides epidemiological evidence of a dose-dependent relationship between exposure risk and severity of illness, which may partially explain why pauci-/asymptomatic EBOV infection, less severe disease, and unrecognized EVD occurs.