COVID-19 vaccine safety: Background incidence rates of anaphylaxis, myocarditis, pericarditis, Guillain-Barré Syndrome, and mortality in South Korea using a nationwide population-based cohort study.

BACKGROUND: To properly assess an association between vaccines and specific adverse events requires a comparison between the observed and background rates; however, studies in South Korea are currently limited. Therefore, in this study, we estimated the background incidence of anaphylaxis, myocarditis, pericarditis, Guillain-Barré syndrome (GBS), and mortality in South Korea. METHODS: A retrospective cohort study was conducted using the National Sample Cohort (NSC) data. Using NSC, the background incidence rate was estimated by dividing the number of episodes during 2009-2019 by the total population by year and then multiplying by 100,000. Using Statistics Korea data, the background mortality rate was estimated by dividing the number of deaths, during 2009-2019 by the standard population for that year and then multiplying by 100,000. Using background mortality rates, we predicted mortality rates for 2021 using autoregressive integrated moving average models. Further, the expected mortality rates were compared with observed mortality rates. RESULTS: The age-adjusted incidence rate (AIR) of anaphylaxis increased from 4.28 to 22.90 cases per 100,000 population (p = 0.003); myocarditis showed no significant increase, changing from 0.56 to 1.26 cases per 100,000 population (p = 0.276); pericarditis increased from 0.94 to 1.88 cases per 100,000 population (p = 0.005); and GBS increased from 0.78 to 1.21 cases per 100,000 population (p = 0.013). The age-adjusted mortality rate decreased from 645.24 to 475.70 deaths per 100,000 population (p <0.001). The 2021 observed/expected mortality rates for overall (ratio: 1.08, 95% confidence interval [CI]: 1.07-1.08), men (ratio: 1.07, 95% CI: 1.07-1.08), and women (ratio: 1.08, 95% CI: 1.07-1.09), were all significantly higher. When stratified by age group, those aged ≥80 (ratio: 1.16, 95% CI: 1.15-1.17), 60-69 (ratio: 1.11, 95% CI: 1.10-1.13), and 20-29 years old (ratio: 1.07, 95% CI: 1.02-1.13) were also significantly higher. CONCLUSION: Through the estimation of background rates related to anaphylaxis, myocarditis, pericarditis, GBS, and mortality, we established a reference point for evaluating the potential excess occurrence of adverse events following COVID-19 vaccination. This reference point serves as substantive evidence supporting the safety profile of COVID-19 vaccines.

Incidence and risk factors of COVID-19 in a tertiary hospital and the effectiveness of booster vaccination among health care workers: A retrospective cohort study, January 2020 to June 2022.

BACKGROUND: Health care workers (HCWs) face a higher risk of infection and may transmit pathogens to patients during a pandemic. This study aims to evaluate infection-control measures by analyzing the incidence and risk factors of COVID-19 and estimating vaccine effectiveness (VE) at a tertiary hospital in Seoul, Republic of Korea. METHODS: This study included 2,516 HCWs from January 1, 2020, to June 30, 2022. Data were analyzed to determine the incidence density and cumulative incidence; the results were compared by the age- and gender-specific standardized incidence ratios (SIR). VE was estimated with multivariate Cox proportional-hazard models as 1-adjusted hazard ratio × 100%. RESULTS: SIR indicated a lower COVID-19 risk in the hospital population than in the general Korean population (SIR, 0.81; 95% confidence interval [CI]: 0.76-0.87). Multivariate Cox analysis indicated that, compared to doctors, nonmedical service supporters and other HCWs (excluding doctors and nurses) were high-risk groups (adjusted hazard ratio [95% CI], 1.72 [1.04-2.83] and 1.76 [1.20-2.58], respectively). Compared to the outpatient unit, the emergency department was a high-risk department (1.70 [1.16-2.50]). The VE of the booster dose was 55.47%, compared to no or incomplete vaccination (95% CI: 22.63-74.37). CONCLUSIONS: Besides encouraging HCWs vaccination, effective infection-control measures should target high-risk groups and departments.

Effects of Severe Acute Respiratory Syndrome Coronavirus Vaccination on Reinfection: A Community-Based Retrospective Cohort Study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is a disease that is characterized by frequent reinfection. However, the factors influencing reinfection remain poorly elucidated, particularly regarding the effect of COVID-19 vaccination on preventing reinfection and its effects on symptomatology and the interval until reinfection. METHODS: This retrospective cohort study examined patients with severe acute respiratory syndrome coronavirus reinfection between January 2020 and February 2022. This study included patients aged >17 years who were reinfected at least 90 days between two infections with severe acute respiratory syndrome coronavirus. The main outcome measure was a reduction in symptoms during reinfection, and reinfection interval. RESULTS: Overall, 712 patients (average age: 40.52 ± 16.41 years; 312 males) were included. The reduction rate of symptoms at reinfection than that at first infection was significantly higher in the vaccinated group than in the unvaccinated group (p < 0.001). The average reinfection interval was 265.81 days. The interval between the first and second infection was 63.47 days longer in the vaccinated group than in the unvaccinated group. The interval was also 57.23 days, significantly longer in the asymptomatic group than in the symptomatic group (p < 0.001). CONCLUSIONS: Besides its role in preventing severe acute respiratory syndrome coronavirus infection, vaccination reduces the rate of symptomatic reinfection and increases the reinfection interval; thus, it is necessary to be vaccinated even after a previous infection. The findings may inform the decision to avail COVID-19 vaccination.

Gender Inequalities in Mental Health During the COVID-19 Pandemic: A Population-based Study in Korea.

OBJECTIVES: This study explored the effect of the coronavirus disease 2019 (COVID-19) pandemic on psychosocial stress in prime working-age individuals in Korea, focusing on gender inequalities. We hypothesized that the impact of COVID-19 on mental health would differ by age and gender, with younger women potentially demonstrating heightened vulnerability relative to men. METHODS: The study involved data from the Korea Community Health Survey and included 319 592 adults aged 30 years to 49 years. We employed log-binomial regression analysis, controlling for variables including age, education, employment status, marital status, and the presence of children. The study period included 3 phases: the period prior to the COVID-19 outbreak (pre-COVID-19), the early pandemic, and the period following the introduction of vaccinations (post-vaccination). RESULTS: The findings indicated that women were at a heightened risk of psychosocial stress during the early pandemic (relative risk [RR], 1.01; 95% confidence interval [CI], 0.98 to 1.05) and post-vaccination period (RR, 1.07; 95% CI, 1.04 to 1.10) compared to men. This pattern was prominent in urban women aged 30-34 years (pre-COVID-19: RR, 1.06; 95% CI, 1.02 to 1.10; early pandemic: RR, 1.16; 95% CI, 1.08 to 1.25; post-vaccination period, RR, 1.22; 95% CI, 1.14 to 1.31). CONCLUSIONS: The COVID-19 pandemic has exerted unequal impacts on psychosocial stress among prime working-age individuals in Korea, with women, particularly those in urban areas, experiencing a heightened risk. The findings highlight the importance of addressing gender-specific needs and implementing appropriate interventions to mitigate the psychosocial consequences of the pandemic.

Cook with Different Pots, but Similar Taste? Comparison of Phase Angle Using Bioelectrical Impedance Analysis According to Device Type and Examination Posture.

Bioelectrical impedance analysis (BIA) is gaining popularity as a tool for body composition assessment. Although BIA has been studied and validated in different populations, age groups, and clinical settings, including critically ill patients, there are concerns about BIA reproducibility and reliability for different device types and postures. This study aimed to evaluate the reliability of BIA using different devices, postures, and lead types. Cross-sectional observational data were collected from 74 healthy volunteers (32 women, 42 men). We used two types of devices, three types of postures (standing, sitting, and lying), and two lead types (clamp lead and adhesive lead) to measure the whole-body phase angle (phA) at a single frequency of 50 kHz. The measurements were validated using the intraclass correlation coefficient (ICC) and Bland-Altman plot analysis. All phA measurements recorded using the two types of devices, three different postures, and two types of leads were equivalent (mean ICC = 0.9932, 95% confidence interval (CI) 0.9905-0.0053, p < 0.001). The average mean difference in phA was 0.31 (95% CI 0.16-0.46). The largest phA value was measured using BWA with an adhesive-type lead in the supine position. There were no differences between the standing and sitting positions. We compared the consistency and reliability of phA using two devices, two lead types, and three postures. Seven different phA were interchangeable in healthy volunteers.

Assessment of severity scoring systems for predicting mortality in critically ill patients receiving continuous renal replacement therapy.

The incidence of acute kidney injury (AKI) is increasing every year and many patients with AKI admitted to the intensive care unit (ICU) require continuous renal replacement therapy (CRRT). This study compared and analyzed severity scoring systems to assess their suitability in predicting mortality in critically ill patients receiving CRRT. Data from 612 patients receiving CRRT in four ICUs of the Korea University Medical Center between January 2016 and November 2018 were retrospectively collected. The mean age of all patients was 67.6 ± 14.8 years, and the proportion of males was 59.6%. The endpoints were in-hospital mortality and 7-day mortality from the day of CRRT initiation to the date of death. The Program to Improve Care in Acute Renal Disease (PICARD), Demirjian's, Acute Physiology and Chronic Health Evaluation (APACHE) II, Simplified Acute Physiology Score (SAPS) 3, Sequential Organ Failure Assessment (SOFA), Multiple Organ Dysfunction Score (MODS), and Liano's scores were used to predict mortality. The in-hospital and 7-day mortality rates in the study population were 72.7% and 45.1%, respectively. The area under the receiver operator characteristic curve (AUROC) revealed the highest discrimination ability for Demirjian's score (0.770), followed by Liano's score (0.728) and APACHE II (0.710). The AUROC curves for the SAPS 3, MODS, and PICARD were 0.671, 0.665, and 0.658, respectively. The AUROC of Demirjian's score was significantly higher than that of the other scores, except for Liano's score. The Hosmer-Lemeshow test on Demirjian's score showed a poor fit in our analysis; however, it was more acceptable than general severity scores. Kidney-specific severity scoring systems showed better performance in predicting mortality in critically ill patients receiving CRRT than general severity scoring systems.

Signal detection of COVID-19 vaccines adverse events using spontaneous reports from South Korea.

PURPOSE: Studies on the detection of COVID-19 vaccine signals in South Korea are insufficient. Therefore, to investigate adverse events (AEs) that might be associated with COVID-19 vaccines, signals were detected using spontaneous reports from South Korea. We compared the signals with the vaccine insert lists of the regulators in the four countries. METHODS: Spontaneous reports from 62 sites were collected by the National Medical Center between January 2013 and May 2022. A descriptive analysis of AEs associated with COVID-19 vaccines (Pfizer, Moderna, AstraZeneca, and Janssen) was performed, and the proportional reporting ratio, reporting odds ratio, and information component were calculated. We performed five analyses, with five cases and one control group. RESULTS: During the study period, 68 355 cases were reported, of which 12 485 were COVID-19 vaccine AEs. Injection site pain (2198 cases, 17.6%), myalgia (1552 cases, 12.4%), headache (1145 cases, 9.2%), pyrexia (1003 cases, 8.0%), and fatigue (735 cases, 5.9%) were frequently reported. When comparing all COVID-19 vaccines with other viral vaccines, 20 signals were detected, of which cachexia, dyspepsia, abdominal discomfort, and mood swings were not listed on the vaccine inserts in all four countries. Overall, 20, 17, 29, and 9 signals were detected in vaccines developed by Pfizer, Moderna, AstraZeneca, and Janssen, respectively. CONCLUSIONS: Based on a disproportionate analysis of COVID-19 vaccine AEs using spontaneous reports from South Korea, different signals were detected for each vaccine manufacturer.

Health behaviors and the risk of COVID-19 incidence: A Bayesian hierarchical spatial analysis.

OBJECTIVES: Effective infection control measures, based on a sound understanding of geographical community-specific health behavioral characteristics, should be implemented from the early stage of disease transmission. However, few studies have explored health behaviors as a possible contributor to COVID-19 infection in the spatial context. We investigated health behaviors as potential factors of COVID-19 incidence in the early phase of transmission in the spatial context. METHODS: We extracted COVID-19 cumulative case data as of February 25, 2021-one day prior to nationwide COVID-19 vaccination commencement-regarding health behaviors and covariates, including health condition and socio-economic factors, at the municipal level from publicly available datasets. The spatial autocorrelation of incidence was analyzed using Global Moran's I statistics. The associations between health behaviors and COVID-19 incidence were examined using Besag-York-Mollie models to deal with spatial autocorrelation of residuals. RESULTS: The COVID-19 incidence had positive spatial autocorrelation across South Korea (I = 0.584, p = 0.001). The results suggest that individuals vaccinated against influenza in the preceding year had a negative association with COVID-19 incidence (relative risk=0.913, 95 % Credible Interval=0.838-0.997), even after adjusting for covariates. CONCLUSIONS: Our ecological study suggests an association between COVID-19 infection and health behaviors, especially influenza vaccination, in the early stage of COVID-19 transmission at the municipal level.

Epidemiology and Transmission Dynamics of Infectious Diseases and Control Measures.

The epidemiology and transmission dynamics of infectious diseases must be understood at the individual and community levels to improve public health decision-making for real-time and integrated community-based control strategies. Herein, we explore the epidemiological characteristics for assessing the impact of public health interventions in the community setting and their applications. Computational statistical methods could advance research on infectious disease epidemiology and accumulate scientific evidence of the potential impacts of pharmaceutical/nonpharmaceutical measures to mitigate or control infectious diseases in the community. Novel public health threats from emerging zoonotic infectious diseases are urgent issues. Given these direct and indirect mitigating impacts at various levels to different infectious diseases and their burdens, we must consider an integrated assessment approach, 'One Health', to understand the dynamics and control of infectious diseases.

Association between Climate Factors and Dengue Fever in Asuncion, Paraguay: A Generalized Additive Model.

Dengue fever has been endemic in Paraguay since 2009 and is a major cause of public-health-management-related burdens. However, Paraguay still lacks information on the association between climate factors and dengue fever. We aimed to investigate the association between climatic factors and dengue fever in Asuncion. Cumulative dengue cases from January 2014 to December 2020 were extracted weekly, and new cases and incidence rates of dengue fever were calculated. Climate factor data were aggregated weekly, associations between dengue cases and climate factors were analyzed, and variables were selected to construct our model. A generalized additive model was used, and the best model was selected based on Akaike information criteria. Piecewise regression analyses were performed for non-linear climate factors. Wind and relative humidity were negatively associated with dengue cases, and minimum temperature was positively associated with dengue cases when the temperature was less than 21.3 °C and negatively associated with dengue when greater than 21.3 °C. Additional studies on dengue fever in Asuncion and other cities are needed to better understand dengue fever.

Risk Prediction of Three Different Subtypes of Highly Pathogenic Avian Influenza Outbreaks in Poultry Farms: Based on Spatial Characteristics of Infected Premises in South Korea.

From 2003 to 2017, highly pathogenic avian influenza (HPAI) epidemics, particularly H5N1, H5N8, and H5N6 infections in poultry farms, increased in South Korea. More recently, these subtypes of HPAI virus resurged and spread nationwide, heavily impacting the entire poultry production and supply system. Most outbreaks in poultry holdings were concentrated in the southwestern part of the country, accounting for 58.3% of the total occurrences. This geographically persistent occurrence demanded the investigation of spatial risk factors related to the HPAI outbreak and the prediction of the risk of emerging HPAI outbreaks. Therefore, we investigated 12 spatial variables for the three subtypes of HPAI virus-infected premises [(IPs), 88 H5N1, 339 H5N8, and 335 H5N6 IPs]. Then, two prediction models using statistical and machine learning algorithm approaches were built from a case-control study on HPAI H5N8 epidemic, the most prolonged outbreak, in 339 IPs and 626 non-IPs. Finally, we predicted the risk of HPAI H5N1 and H5N6 occurrence at poultry farms using a Bayesian logistic regression and machine learning algorithm model [extreme gradient boosting (XGBoost) model] built on the case-control study. Several spatial variables showed similar distribution between two subtypes of IPs, although there were distinct heterogeneous distributions of spatial variables among the three IP subtypes. The case-control study indicated that the density of domestic duck farms and the minimum distance to live bird markets were leading risk factors for HPAI outbreaks. The two prediction models showed high predictive performance for H5N1 and H5N6 occurrences [an area under the curve (AUC) of receiver operating characteristic of Bayesian model > 0.82 and XGBoost model > 0.97]. This finding emphasizes that spatial characteristics of the poultry farm play a vital role in the occurrence and forecast of HPAI outbreaks. Therefore, this finding is expected to contributing to developing prevention and control strategies.

Trends of Internet Search Volumes for Major Depressive Disorder Symptoms During the COVID-19 Pandemic in Korea: An Interrupted Time-Series Analysis.

BACKGROUND: The effect of coronavirus disease 2019 (COVID-19) pandemic on public mental health has been increasing. Additionally, the underlying psychological stressors remain unexplored, and few studies have been conducted nationally on the social distancing measures. Therefore, the present study aimed to identify the psychological impacts of the implementation of social distancing measures by analyzing the Internet search trends of major depressive disorder (MDD) symptoms. METHODS: Using Naver® Trends' relative search volumes (RSVs), we analyzed the average search volumes and trend changes of 16 terms, adopted from the Diagnostic and Statistical Manual of Mental Disorders-5 criteria for diagnosing MDD. An interrupted time-series analysis was performed using the data from January 1, 2016 to December 31, 2020. Furthermore, changes in RSVs, according to the intensity of the social distancing measures implemented from January 1 to December 31, 2020, were determined using Wilcoxon rank sum tests. RESULTS: Of the 16 terms, the search trends of 'feeling guilty' (P < 0.001) and 'wanting to die' (P = 0.002) showed a significant increase as of February 29, 2020, when the social distancing measures were officially implemented. Additionally, the average search volumes for 'hopelessness' (P = 0.003), 'sexual desire' (P < 0.001), 'insomnia' (P = 0.002), 'hypersomnia' (P < 0.001), 'restlessness' (P < 0.001), and 'feeling lethargic' (P < 0.001) increased significantly. Moreover, gender analysis showed that the average search volume of 'depressed mood' (P = 0.033) and the trend of 'impaired concentration' (P < 0.001) increased in males only. However, the average search volume of 'feeling lethargic' (P = 0.001) and the trend of 'feeling guilty' (P = 0.001) increased in females only. The average search volumes for 'depressed mood' (P < 0.001), 'impaired concentration' (P = 0.038), and 'indecisiveness' (P < 0.001) were significantly higher during the enforcement of level 2 or higher social distancing measures. CONCLUSION: Our results reported the negative effect of COVID-19 preventive measures on public mental health in South Korea, especially for MDD symptoms. Moreover, the findings suggested the utility of Naver Trends as a feasible big data source to assess future mental health crises.

Ambient Air Pollution and Kawasaki Disease in Korean Children: A Study of the National Health Insurance Claim Data.

Background Kawasaki disease (KD) is a systemic vasculitis of unknown etiology that primarily affects children under 5 years of age. Some researchers suggested a potential triggering effect of air pollution on KD, but the findings are inconsistent and limited by small sample size. We investigated the association between ambient air pollution and KD among the population of South Korea younger than 5 years using the National Health Insurance claim data between 2007 and 2019. Methods and Results We obtained the data regarding particulate matter ≤10 or 2.5 µm in diameter, nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone from 235 regulatory monitoring stations. Using a time-stratified case-crossover design, we performed conditional logistic regression to estimate odds ratios (OR) of KD according to interquartile range increases in each air pollutant concentration on the day of fever onset after adjusting for temperature and relative humidity. We identified 51 486 children treated for KD during the study period. An interquartile range increase (14.67 µg/m3) of particulate matter ≤2.5 µm was positively associated with KD at lag 1 (OR, 1.016; 95% CI, 1.004-1.029). An interquartile range increase (2.79 ppb) of sulfur dioxide concentration was associated with KD at all lag days (OR, 1.018; 95% CI, 1.002-1.034 at lag 0; OR, 1.022; 95% CI, 1.005-1.038 at lag 1; OR, 1.017; 95% CI, 1.001-1.033 at lag 2). Results were qualitatively similar in the second scenario of different fever onset, 2-pollutant model and sensitivity analyses. Conclusions In a KD-focused national cohort of children, exposure to particulate matter ≤2.5 µm and sulfur dioxide was positively associated with the risk of KD. This finding supports the triggering role of ambient air pollution in the development of KD.

Epidemiology and evaluation of adverse drug reactions in a Korean hospital database for spontaneous reports in the period 2009 to 2018.

OBJECTIVE: To evaluate the epidemiology of adverse drug reactions (ADRs) in the Korean population and to identify their characteristics and factors affecting their severity. MATERIALS AND METHODS: The analysis was based on the ADRs reported to the Seoul National University Hospital between 2009 and 2018. Statistical assessment (SPSS Statistics 25) included frequency analysis and the χ2-test. Risk factors were assessed using logistic regression analysis. Results were considered significant at p < 0.05. RESULTS: A total of 44,122 cases were analyzed of which 24,801 (56.2%) cases concerned females and 19,321 (43.8%) males. A total of 47% of cases involved persons aged between 50 and 79 years. Antineoplastic agents, immunomodulating agents, and systemically administered anti-infective agents accounted for 57.6% of all drugs reported. Gastro-intestinal system disorders accounted for the largest proportion (25.8%) of adverse drug reactions reported. A total of 3,429 (7.8%) ADRs were reported as being in the category severe. Multivariate analysis showed that the risk of an ADR being reported as severe is higher in males than in females (OR = 1.25, 95% CI: 1.16 - 1.35), and higher in those aged 0 - 4 years (OR = 1.74, 95% CI: 1.46 - 2.08), in those aged 5 - 19 years (OR = 1.19, 95% CI: 1.07 - 1.31), and in those aged 65 years and over (OR = 1.26, 95% CI: 1.16 - 1.37), compared to those aged 20 - 64 years. DISCUSSION AND CONCLUSION: From a public health perspective, ADRs are important because they are preventable. Important determinants, such as differences in specific age groups and drug classes, for the occurrence of ADRs and the occurrence of severe ADRs in particular, were identified. These determinants need to be carefully monitored in both private medical practices, clinics and hospitals. This monitoring of specific groups will involve close attention factors associated with gender, age group, and drug classes.

Socioeconomic Inequalities in COVID-19 Incidence During Different Epidemic Phases in South Korea.

Objective: Area-level socioeconomic status (SES) is associated with coronavirus disease 2019 (COVID-19) incidence. However, the underlying mechanism of the association is context-specific, and the choice of measure is still important. We aimed to evaluate the socioeconomic gradient regarding COVID-19 incidence in Korea based on several area-level SES measures. Methods: COVID-19 incidence and area-level SES measures across 229 Korean municipalities were derived from various administrative regional data collected between 2015 and 2020. The Bayesian negative binomial model with a spatial autocorrelation term was used to estimate the incidence rate ratio (IRR) and relative index of inequality (RII) of each SES factor, with adjustment for covariates. The magnitude of association was compared between two epidemic phases: a low phase (<100 daily cases, from May 6 to August 14, 2020) and a rebound phase (>100 daily cases, from August 15 to December 31, 2020). Results: Area-level socioeconomic inequalities in COVID-19 incidence between the most disadvantaged region and the least disadvantaged region were observed for nonemployment rates [RII = 1.40, 95% credible interval (Crl) = 1.01-1.95] and basic livelihood security recipients (RII = 2.66, 95% Crl = 1.12-5.97), but were not observed for other measures in the low phase. However, the magnitude of the inequalities of these SES variables diminished in the rebound phase. A higher area-level mobility showed a higher risk of COVID-19 incidence in both the low (IRR = 1.67, 95% Crl = 1.26-2.17) and rebound phases (IRR = 1.28, 95% Crl = 1.14-1.44). When SES and mobility measures were simultaneously adjusted, the association of SES with COVID-19 incidence remained significant but only in the low phase, indicating they were mutually independent in the low phase. Conclusion: The level of basic livelihood benefit recipients and nonemployment rate showed social stratification of COVID-19 incidence in Korea. Explanation of area-level inequalities in COVID-19 incidence may not be derived only from mobility differences in Korea but, instead, from the country's own context.

Epidemiologic Characteristics and Case Fatality Rate of Vibrio vulnificus Infection: Analysis of 761 Cases From 2003 to 2016 in Korea.

BACKGROUND: Vibrio vulnificus infection is a highly fatal disease resulting from the consumption of raw or undercooked seafood and exposure to seawater containing the organism. It has been a nationally notifiable disease since 2000 in Korea. The aims of this study were to assess the trends in the incidence of V. vulnificus infection and its case fatality rate and to determine the epidemiologic characteristics to effectively prevent infection and lower mortality. METHODS: We analyzed the incidence trends of V. vulnificus infection by year, month, and region in 913 cases reported to the Korea Centers for Disease Control and Prevention (KCDC, currently Korea Disease Control and Prevention Agency) by the National Infectious Disease Surveillance System from 2001 to 2016. We analyzed the number of patients with V. vulnificus infection who were under the National Health Insurance Service (NHIS) and whose coastal seawater temperature data were provided by the Korea Oceanographic Data Center of the National Institute of Fisheries Science. Epidemiological investigations were followed up and analyzed for 761 patients from 2003 to 2016. A total of 152 patients who were not followed up were excluded from the analysis. The case fatality rate was analyzed for 325 cases reported to the KCDC from 2011 to 2016. RESULTS: The mean incidence of V. vulnificus infection was 0.12 per 100,000 people, and the highest incidence was reported in September (41.1%) during the study period. The incidence rate per 100,000 people was the highest in Jeonnam (8.23). The number of patients who claimed to the NHIS was the highest in September (105 patients). The average seawater temperature was the highest at 24.1°C in August, and the average seawater temperature from August to October, when many cases occurred, was 22.4°C. The male-to-female ratio was 6:1, and 96.4% of the patients were aged ≥ 40 years. Of the patients, 96.1% had underlying diseases, the most common of which was liver cirrhosis (56.3%). The case fatality rate was 48.9%. CONCLUSION: The occurrence of V. vulnificus infection showed distinct seasonality, with a large number of cases occurring in the months when the seawater temperature was high; there were also distinct geographical characteristics. The incidence of V. vulnificus infection and mortality rates have not decreased for decades, and it is still an important public health problem with a high fatality rate.

Self-Quarantine Noncompliance During the COVID-19 Pandemic in South Korea.

OBJECTIVES: In South Korea, many individuals were self-quarantined for the coronavirus disease 2019 (COVID-19) after the quarantine criteria were extended to all overseas travelers. This study was conducted to identify the noncompliance rate of self-quarantine for COVID-19 cases and assess the impact of a 1-strike out policy and an increased amount of penalty for the violating self-quarantine in South Korea. METHODS: The self-quarantine noncompliance rate for COVID-19 was examined using publicly available data. We collected the daily number of quarantine and quarantine violation cases from March 22 to June 10, 2020. A Poisson regression analysis was conducted to identify the impact of additional sanctions for the quarantine violation. RESULTS: The median number of individuals quarantined per day was 36,561 (interquartile range, 34,408-41,961). The median number of daily self-quarantine violations was 6 (range, 0-13). The median rate of self-quarantine violations was 1.6 per 10,000 self-quarantined individuals (range, 0.0-8.0 per 10,000 self-quarantined individuals). The additional sanction has no significant impact on the number of violations among quarantine individuals (P = 0.99). CONCLUSIONS: The additional sanction for the violation of quarantined individuals did not reduce the self-quarantine violations. Further studies are warranted to strengthen the compliance of self-quarantine for future pandemics.

Preventive effect of on-farm biosecurity practices against highly pathogenic avian influenza (HPAI) H5N6 infection on commercial layer farms in the Republic of Korea during the 2016-17 epidemic: A case-control study.

Highly pathogenic avian influenza virus (HPAIv) H5N6 has destructive consequences on the global poultry production system. Recently, a growing number of layer farms have been heavily damaged from the HPAIv epidemic due to the increased virulence of the virus and the intensification of the production system. Therefore, stakeholders should implement effective preventive practices at the farm level that are aligned with contingency measures at the national level to minimize poultry losses. However, numerous biosecurity protocols for layer farm workers to follow have been developed, impeding efficient prevention and control. Furthermore, the effectiveness of biosecurity practices varies with the geographical condition and inter-farm contact structures. Hence, the objective of our study was to examine the preventive effect of five biosecurity actions commonly practiced at layer farms in the Republic of Korea against HPAIv H5N6: (i) fence installation around a farm, ii) rodent control inside a farm; iii) disinfection booth for visitors for disinfection protocols, iv) an anterior room in the sheds before entering the bird area and v) boots changes when moving between sheds in the same farm. We conducted a case-control study on 114 layer case farms and 129 layer control farms during the 2016-17 HPAI epidemic. The odds ratios for five on-farm biosecurity practices implemented in those study groups were estimated as a preventive effect on the HPAI infection with covariates, including seven geographical conditions and three network metrics using Bayesian hierarchical logistic regression and geographical location weighted logistic regression. The results showed that the use of a disinfection booth for personnel reduced the odds of HPAIv H5N6 infection (adjusted odds ratio [AOR] = 0.002, 95 % credible interval [CrI] = 0.00007 - 0.025) with relatively small spatial variation (minimum AOR - maximum AOR: 0.084-0.263). Changing boots between sheds on the same farm reduced the odds of HPAIv H5N6 infection (AOR = 0.160, 95 % CrI = 0.024-0.852) with relatively wide spatial variation (minimum AOR - maximum AOR = 0.270-0.688). Therefore, enhanced personnel biosecurity protocols at the farm of entry for layer farms is recommended to effectively prevent and respond to HPAIv H5N6 infection under different local condition. Our study provides an important message for layer farmers to effectively implement on-farm biosecurity actions against HPAIv H5N6 infection at their farms by setting priorities based on their spatial condition and network position.

Spatiotemporal risk assessment for avian influenza outbreak based on the dynamics of habitat suitability for wild birds.

Highly pathogenic avian influenza (HPAI) has predominantly damaged the poultry industry worldwide. The fundamental prevention and control strategy for HPAI includes early detection and timely intervention enforcement through a systematic surveillance system for wild birds based on the ecological understanding of the dynamics of wild birds' movements. Our study aimed to develop a spatiotemporal risk assessment model for avian influenza (AI) infection in wild birds to empower surveillance information for a contingency strategy. For this purpose, first, we predicted the monthly habitat suitability of seven waterfowl species, using 227,671 Global Positioning System (GPS) tracking records of 562 birds from 2014 to 2018 in the Republic of Korea (ROK). Then, that predicted habitat suitability and 421 coordinates of AI detection sites in wild birds were used to build the risk assessment model. Subsequently, we compared the monthly predicted risk of avian influenza virus (AIv) identification in wild birds between case and non-case poultry farms with HPAI H5N6 outbreak in the ROK between 2016 and 2017. The results reported considerable variation of monthly habitat suitability of seven waterfowls and the impact of predicting AI occurrences in wild birds. The high habitat suitability for spot-billed ducks (contribution rate in November = 40.9%) and mallards (contribution rate in January = 34.3%) significantly contributed to predicting the average risk of AIv identification in wild birds, with high predictive performance [the monthly mean of area under the curve (AUC) = 0.978]. Moreover, our model showed that the averaged risk of identification AI in wild birds was significantly higher in HPAI infected premises, with infected domestic duck holdings exhibiting a significantly higher risk than the chicken farms in November. This study suggests that animal health authority establishes a risk-based HPAI surveillance system grounded on the ecological nature of wild birds to improve the effectiveness of prevention and preparedness of emerging epidemics.