Sierra Leone is the most severely affected country by an unprecedented outbreak of Ebola virus disease (EVD) in West Africa. Although successfully contained, the transmission dynamics of EVD and the impact of interventions in the country remain unclear. We established a database of confirmed and suspected EVD cases from May 2014 to September 2015 in Sierra Leone and mapped the spatiotemporal distribution of cases at the chiefdom level. A Poisson transmission model revealed that the transmissibility at the chiefdom level, estimated as the average number of secondary infections caused by a patient per week, was reduced by 43% [95% confidence interval (CI): 30%, 52%] after October 2014, when the strategic plan of the United Nations Mission for Emergency Ebola Response was initiated, and by 65% (95% CI: 57%, 71%) after the end of December 2014, when 100% case isolation and safe burials were essentially achieved, both compared with before October 2014. Population density, proximity to Ebola treatment centers, cropland coverage, and atmospheric temperature were associated with EVD transmission. The household secondary attack rate (SAR) was estimated to be 0.059 (95% CI: 0.050, 0.070) for the overall outbreak. The household SAR was reduced by 82%, from 0.093 to 0.017, after the nationwide campaign to achieve 100% case isolation and safe burials had been conducted. This study provides a complete overview of the transmission dynamics of the 2014−2015 EVD outbreak in Sierra Leone at both chiefdom and household levels. The interventions implemented in Sierra Leone seem effective in containing the epidemic, particularly in interrupting household transmission.Ebola virus disease | spatiotemporal modeling | household transmission | secondary attack rate | intervention effectiveness

ObjectivesTo assess the public’s knowledge, attitudes and practices about the novel coronavirus in Sierra Leone to inform an evidence-based communication strategy around COVID-19.DesignNationwide, cross-sectional Knowledge, Attitudes and Practices survey.Setting56 randomly selected communities in all 14 districts in Sierra Leone.Participants1253 adults aged 18 years and older of which 52% were men.Main outcome measuresWe calculated proportions of core indicators (awareness, knowledge, risk perception, practices). A composite variable for knowledge (based on seven variables) was created, and categorised into low (0–2 correct), medium (3–4) and high (5–7). Predictors of knowledge were analysed with multilevel ordinal regression models. Associations between information sources, knowledge and two practices (washing hands with soap and avoiding crowds) were analysed using multilevel logistic regression models.ResultsWe found that 75% of the respondents felt at moderate or great risk of contracting coronavirus. A majority (70%) of women did not know you can survive COVID-19, compared with 61% of men. 60% of men and 54% of women had already taken action to avoid infection with the coronavirus, mostly washing hands with soap and water (87%). Radio (73%) was the most used source for COVID-19 information, followed by social media (39%). Having a medium or high level of knowledge was associated with higher odds of washing hands with soap (medium knowledge: adjusted OR (AOR) 2.1, 95% CI 1.0 to 4.4; high knowledge: AOR 4.6, 95% CI 2.1 to 10.2) and avoiding crowds (medium knowledge: AOR 2.0, 95% CI 1.1 to 3.6; high knowledge: AOR 2.3, 95% CI 1.2 to 4.3).ConclusionsThis study shows that in the context of COVID-19 in Sierra Leone, there is a strong association between knowledge and practices. Because the knowledge gap differs between genders, regions, educational levels and age, it is important that messages are specifically targeted to these core audiences.

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