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INTRODUCTION: While the reduction in influenza cases in the Northern hemisphere in 2020 has been widely reported, the influenza transmission dynamics in the Southern hemisphere remain uncharacterized. METHODS: This study analysed the change in influenza-positive proportion (IPP) between 2010-2019 and 2020 in countries in the Southern hemisphere with ≤40% missing IPP data in FluNet to assess how coronavirus disease 2019 (COVID-19) relates to influenza activity. The analysis considered the incidence of COVID-19 reported by the World Health Organization and the implementation date of non-pharmaceutical interventions (NPIs) reported by the Oxford COVID-19 Government Response Tracker. RESULTS: In each of the seven included countries, the average IPP was lower in 2020 than in 2010-2019 (P < 0.01), with the largest difference being 31.1% (95% confidence interval 28.4-33.7%). In Argentina, Bolivia, Chile and South Africa, higher IPPs were observed during epidemiological weeks 4-16 in 2020 compared with the same weeks in 2010-2019. The IPP increased after NPIs were implemented in Argentina and South Africa, but started to decline in Bolivia, Chile, Madagascar and Paraguay before NPI implementation. CONCLUSIONS: Influenza burden and activity decreased in 2020 in the Southern hemisphere. The temporal decline in influenza activity varied between countries.

Background Despite the etiology of Kawasaki Disease (KD) remains unknown, identifying spatiotemporal clusters of KD could support its hypothesis to be infectious disease. However, spatiotemporal clusters of KD have never been reported in South Korea. Therefore, this study aims to analyse the spatiotemporal patterns of KD in South Korea using national representative data. Methods We extracted epidemiologic-week (Epi-week) based KD case (ICD-10-CM code, M303) from 2008-2017 national health insurance service data in municipal level. To determine whether spatial autocorrelation and municipal-level clusters exist, year, sex, and age group ( Results A total of 98,503 cases of KD were reported in 2008-2017 (aged Conclusions South Korea had steady increase in KD incidence since 2008 and municipal-level clusters throughout 2008-2017. Key messages Kawasaki disease in South Korea had spatiotemporal patterns.

Background The prevalence of dementia is increasing worldwide; and dementia deaths are also increasing. In South Korea, deaths from Alzheimer's disease (AD) ranked 9th in the 2018 cause of death statistics, and the ranking has risen. Methods We collected 2009 to 2018 AD deaths and related data from Statistics Korea and Community Health Survey. SaTScan software was used for detecting and evaluating the clusters with high risk in AD deaths, and R version 4.0.3 was used for mapping and analysis of affecting factors. Results A total of 39,412 people died from AD during 10 years in Korea, 7.7 per 100,000 inhabitants. While 98.7% of deaths were above-65 age, the proportion of under 65 was also rising. The global Moran index of 10 years’ AD deaths was 0.2 (P Conclusions Some clusters of AD deaths were identified, and they were influenced by institutional factors. It is necessary that the local government considers characteristics of each region when implementing the dementia policies. Key messages AD deaths in South Korea were increasing from 2009 to 2018, and their clusters were observed in southern regions. AD deaths in 2018 were influenced by dementia-related policies.

Background Personal health behaviours, which rely on community characteristics, could affect individual vulnerability on disease infection. Due to insufficient study to examine health behaviours as risk factors of COVID-19 infection, we conducted municipal level spatial analysis to investigate association between health behaviours and COVID-19 incidence. Methods We extracted cumulative COVID-19 incidence data from January 20th 2020 to February 25th 2021, health behaviours, health condition, socio-economic factors, and covariates in municipal level from publicly available dataset. We chose variables, which were standardized, considering multicollinearity (VIF Results The mean cumulative COVID-19 incidence per 10,000 population among 229 municipality was 13.73 (Standard deviation=11.43). iCAR model (DIC=2,825.3) outperformed BYM model (DIC=14,009.4). The results of iCAR model highlighted that incidence was associated with dental hygiene practice (incidence risk ratios [IRR]=0.92, 95% Credible Interval [CI]=0.85–1.00), whether tried to be thin (IRR=1.10, 95% CI = 1.00–1.20), proportion of medical personnel (IRR=1.09, 95% CI = 1.01–1.17), and volume of public transportation (IRR=1.19, 95% CI = 1.05–1.35), even after adjusting for various confounding factors. Conclusions Municipality with lower cumulative incidence was likely to have more people who practiced to keep dental hygiene and less people who tried to be thin. Key messages Municipal level spatial analysis resulted that health behaviours were associated with COVID-19 incidence in South Korea.

Although coronavirus disease 2019 (COVID-19) is an ongoing pandemic, the mean serial interval was measured differently across nations. Through the Korean national COVID-19 contact tracing system, we were able to investigate personal contacts in all symptomatic cases in Korea from January 20 to August 3, 2020. The mean serial interval was calculated by the duration between the symptom onset of the infector and infectee, and became shorter after the case definition changed to include not-imported cases in Korea on February 20, 2020. The mean serial interval before and after this fifth case definition was 6.12 and 3.93 days based on the infectors' symptom onset date, respectively, and 4.02 days in total with the median of 3 days. Older age and women lead to longer serial intervals., Graphical Abstract