Estimating the Risk of COVID-19 Death During the Course of the Outbreak in Korea, February–May 2020

Background: In Korea, a total of 10, 840 confirmed cases of COVID-19 including 256 deaths have been recorded as of May 9, 2020. The time-delay adjusted case fatality risk (CFR) of COVID-19 in Korea is yet to be estimated. Methods: We obtained the daily series of confirmed cases and deaths in Korea reported prior to May 9, 2020. Using statistical methods, we estimated the time-delay adjusted risk for death from COVID-19 in Daegu, Gyeongsangbuk-do, other regions in Korea, as well as the entire country. Results: Our model-based crude CFR fitted the observed data well throughout the course of the epidemic except for the very early stage in Gyeongsangbuk-do; this was partially due to the reporting delay. Our estimates of the risk of death in Gyeongsangbuk-do reached 25.9% (95% Credible Interval (CrI): 19.6%–33.6%), 20.8% (95% CrI: 18.1%–24.0%) in Daegu, and 1.7% (95% CrI: 1.1%–2.5%) in other regions, whereas the national estimate was 10.2% (95% CrI: 9.0%–11.5%). Conclusions: The latest estimates of CFR of COVID-19 in Korea are considerably high, even with the early implementation of public health interventions including widespread testing, social distancing, and delayed school openings. Geographic differences in the CFR are likely influenced by clusters tied to hospitals and nursing homes

Estimating the Risk of Middle East Respiratory Syndrome (MERS) Death During the Course of the Outbreak in the Republic of Korea

Objectives: A large cluster of the Middle East respiratory syndrome (MERS) linked to healthcare setting occurred from May to July 2015 in the Republic of Korea. The present study aimed to estimate the case fatality ratio (CFR) by appropriately taking into account the time delay from illness onset to death. We then compare our estimate against previously published values of the CFR for MERS, i.e., 20% and 40%. Methods: Dates of illness onset and death of the MERS outbreak in the Republic of Korea were extracted from secondary data sources. Using the known distribution of time from illness onset to death and an integral equation model, we estimated the delay-adjusted risk of MERS death for the South Korean cluster. Results: Our most up-to-date estimate of CFR for the MERS outbreak in South Korea was estimated at 20.0% (95% confidence intervals (CI): 14.6, 26.2). During the course of the outbreak, estimate of the CFR in real time appeared to have decreased and become significantly lower than 40%. Conclusions: The risk of MERS death in Korea was consistent with published CFR. The estimate decreased with time perhaps due to time-dependent increase in case ascertainment. Crude ratio of cumulative deaths t

Contact behaviour of children and parental employment behaviour during school closures against the pandemic influenza A (H1N1-2009) in Japan

Objectives: To identify epidemiological determinants of the contact behaviour of children and their impact on parental employment, during school closures that took place over the course of the 2009 pandemic influenza (H1N1-2009) in Japan. Methods: A retrospective survey was conducted in Japanese households between October 2009 and May 2010 by administration of a standardized questionnaire. Demographic and behavioural variables were explored, in association with the frequency with which children left the home and the risk of parents being absent from work during school closures. Results: Data from 882 eligible households were analysed. A total of 181/882 (20.5%) of households reported that children left the home for nonessential reasons during school closures. No impact on parental working hours was reported by 742/882 (84.1%) of households. Univariate analyses showed that the frequency with which children left the home was dependent on age, extent of school closure and requirement for special childcare arrangements. Conclusions: A greater understanding of age-dependent behaviours, during school closures as a consequence of a pandemic, is required. Consideration of a public policy to permit a paid leave of absence from work for parents during school closures may be beneficial; the cost-effectiveness of such a measure should be assessed in future

Real-time Characterization of Risks of Death Associated With the Middle East Respiratory Syndrome (MERS) in the Republic of Korea, 2015

Background: An outbreak of the Middle East respiratory syndrome (MERS), comprising 185 cases linked to healthcare facilities, occurred in the Republic of Korea from May to July 2015. Owing to the nosocomial nature of the outbreak, it is particularly important to gain a better understanding of the epidemiological determinants characterizing the risk of MERS death in order to predict the heterogeneous risk of death in medical settings. Methods: We have devised a novel statistical model that identifies the risk of MERS death during the outbreak in real time. While accounting for the time delay from illness onset to death, risk factors for death were identified using a linear predictor tied to a logit model. We employ this approach to (1) quantify the risks of death and (2) characterize the temporal evolution of the case fatality ratio (CFR) as case ascertainment greatly improved during the course of the outbreak. Results: Senior persons aged 60 years or over were found to be 9.3 times (95 % confidence interval (CI), 5.3–16.9) more likely to die compared to younger MERS cases. Patients under treatment were at a 7.8-fold (95 % CI, 4.0–16.7) significantly higher risk of death compared to other MERS cases. The CFR among patients aged 60 years or older under treatment was estimated at 48.2 % (95 % CI, 35.2–61.3) as of July 31, 2015, while the CFR among other cases was estimated to lie below 15 %. From June 6, 2015, onwards, the CFR declined 0.3-fold (95 % CI, 0.1–1.1) compared to the earlier epidemic period, which may perhaps reflect enhanced case ascertainment following major contact tracing efforts. Conclusions: The risk of MERS death was significantly associated with older age as well as treatment for underlying diseases after explicitly adjusting for the delay between illness onset and death. Because MERS outbreaks are greatly amplified in the healthcare setting, enhanced infection control practices in medical facilities should strive to shield risk groups from MERS exposure

Nature of collective decision-making by simple yes/no decision units Eisuke Hasegawa

The study of collective decision-making spans various fields such as brain and behavioural sciences, economics, management sciences, and artificial intelligence. Despite these interdisciplinary applications, little is known regarding how a group of simple 'yes/no' units, such as neurons in the brain, can select the best option among multiple options. One prerequisite for achieving such correct choices by the brain is correct evaluation of relative option quality, which enables a collective decision maker to efficiently choose the best option. Here, we applied a sensory discrimination mechanism using yes/no units with differential thresholds to a model for making a collective choice among multiple options. The performance corresponding to the correct choice was shown to be affected by various parameters. High performance can be achieved by tuning the threshold distribution with the options' quality distribution. The number of yes/no units allocated to each option and its variability profoundly affects performance. When this variability is large, a quorum decision becomes superior to a majority decision under some conditions. The general features of this collective decision-making by a group of simple yes/no units revealed in this study suggest that this mechanism may be useful in applications across various fields

Development of a scale to measure learners\u27 perceived preferences and benefits of data-driven learning

In spite of researchers\u27 and practitioners\u27 increasing attention to data-driven learning (DDL) and increasing numbers of DDL studies, a multi-item scale to measure learners\u27 attitude toward DDL has not been developed thus far. In the present study, we developed and validated a psychometric scale to measure learners\u27 perceived preferences and benefits of DDL for research and pedagogical purposes. First, we created an item pool by referring to open-ended responses from learners; second, the items were pilot tested with target-level learners of English as a foreign language; and third, with item analyses and exploratory factor analysis, the revised version of the questionnaire was prepared. Finally, the questionnaire was administered, and its psychometric properties were examined with confirmatory factor analysis and fit indices. The final phase also included a measure of task values to explore the convergent evidence of the construct validity of the proposed scale. The results suggest that the scale is a valid measure of learners\u27 attitudes toward DDL, with the hypothesized model providing a good fit with the data. We propose that the scale can be used in future studies that utilize the same type of questionnaire research to facilitate further investigation of DDL. Suggestions for further research are also provided.This study was supported by JSPS KAKENHI Grant Numbers 26704006 and 25284108

Open Access

Cost-effective length and timing of school closure during an influenza pandemic depend on the severit