Incidence, Severity, and Mortality of Influenza During 2010–2020 in Korea: A Nationwide Study Based on the Population-Based National Health Insurance Service Database

Background The epidemiology of influenza is commonly used to understand and establish relevant health policies for emerging respiratory infections, including coronavirus disease 2019 (COVID-19). However, Korea has no confirmed nationwide data on influenza incidence, severity, and mortality rate. Methods We conducted a cross-sectional study to obtain epidemic data on influenza at the national level using National Health Insurance claims data during 2010 to 2020. Influenza cases were defined as 90-day timeframe episodes based on all inpatient and outpatient claims data with disease code J09, J10, and J11. Influenza incidence, severity, and mortality rate were calculated, and logistic regressions were performed to assess the associations of demographic characteristics and comorbidity with influenza-related hospitalization, severe illness, and death. Results There were 0.4–5.9% influenza cases in the population from 2010 to 2020, with 9.7–18.9%, 0.2–0.9%, and 0.03–0.08% hospitalized, used in the intensive care unit, and dead, respectively. Age-standardized incidence and mortality rates were 424.3–6847.4 and 0.2–1.9 per 100,000 population, respectively. While more than half of the influenza cases occurred in populations aged younger than 20 years, deaths in older than 60 years accounted for more than two-thirds of all deaths. Conclusion This study provided the simplest but most important statistics regarding Korean influenza epidemics as a reference. These can be used to understand and manage other new acute respiratory diseases, including COVID-19, and establish influenza-related policies. Graphical

Incidence, Severity, and Mortality of Influenza During 2010-2020 in Korea: A Nationwide Study Based on the Population-Based National Health Insurance Service Database.

BACKGROUND: The epidemiology of influenza is commonly used to understand and establish relevant health policies for emerging respiratory infections, including coronavirus disease 2019 (COVID-19). However, Korea has no confirmed nationwide data on influenza incidence, severity, and mortality rate. METHODS: We conducted a cross-sectional study to obtain epidemic data on influenza at the national level using National Health Insurance claims data during 2010 to 2020. Influenza cases were defined as 90-day timeframe episodes based on all inpatient and outpatient claims data with disease code J09, J10, and J11. Influenza incidence, severity, and mortality rate were calculated, and logistic regressions were performed to assess the associations of demographic characteristics and comorbidity with influenza-related hospitalization, severe illness, and death. RESULTS: There were 0.4-5.9% influenza cases in the population from 2010 to 2020, with 9.7-18.9%, 0.2-0.9%, and 0.03-0.08% hospitalized, used in the intensive care unit, and dead, respectively. Age-standardized incidence and mortality rates were 424.3-6847.4 and 0.2-1.9 per 100,000 population, respectively. While more than half of the influenza cases occurred in populations aged younger than 20 years, deaths in older than 60 years accounted for more than two-thirds of all deaths. CONCLUSION: This study provided the simplest but most important statistics regarding Korean influenza epidemics as a reference. These can be used to understand and manage other new acute respiratory diseases, including COVID-19, and establish influenza-related policies.

Trends in emergency department visits for suicide attempts before and during the COVID-19 pandemic in Korea: A nationwide study, 2016-2021.

BACKGROUND: There is increasing concern that the effects of the COVID-19 pandemic will result in excess suicides by increasing known risk factors, such as suicide attempts. However, evidence on the long-term impacts of COVID-19 on suicide attempts is lacking. We aimed to assess the short- and long-term effects of the COVID-19 pandemic on patients with suicide attempts in emergency departments (EDs) and to evaluate age- and sex-specific differences. METHOD: We conducted nationwide cross-sectional study among patients with suicide attempts in the ED from 2016 to 2021. The trend test were used to determine whether study subjects were affected by changes in ED visits for suicide attempts. We estimated the average annual percentage change (APC) stratified by sex and age groups. RESULTS: The number of ED visits related to suicide attempts increased from 27,581 in 2016 to 37,719 in 2021. In particular, it decreased immediately after the COVID-19 pandemic but increased again in 2021. We identified that the average APC increased by 6.8 % overall, 1.6 % among males, and 10.8 % among females. Moreover, the APC of trend sharply increased in patients aged 10s and 20s. The in-hospital mortality was 3.6 % for females, compared to 9.5 % for males, which showed sex differences. LIMITATIONS: This study was limited to confirming causal relationship based on a descriptive study. CONCLUSIONS: The incidence of suicide attempts in ED has increased in Korea. In particular, there was a sharp increase among women, adolescents and young adults. Patient-tailored treatment and preventive medical system for suicide attempts is important.

Temporal Trends and Characteristics of Adult Patients in Emergency Department Related to Suicide Attempt or Self-Harm in Korea, 2016-2020.

BACKGROUND: The implementation of an effective suicide prevention program requires the identification and monitoring of subpopulations with elevated risks for suicide in consideration of demographic characteristics, to facilitate the development of tailored countermeasures for tackling the risk factors of suicide. We examined the annual trends in emergency department (ED) visits for suicide attempts (SAs) or self-harm and investigated the sex- and age-specific characteristics of individuals who visited the ED for SA and self-harm. METHODS: Data on ED visits for SAs or self-harm in Korea from 2016 to 2020 were extracted from the National Emergency Department Information System and assessed. We evaluated the age-standardized incidence rate of ED visits for SAs or self-harm, and hospital mortality among individuals who visited the ED for SAs or self-harm. In addition, the characteristics of the individuals were compared according to sex and age. RESULTS: We identified 145,963 ED visits for SAs or self-harm (0.42% of the total ED visits) during the study period. The rate of ED visits increased in the youngest age group (19-29 years old), and was more prominent among women (increased by an annual average of 22.5%), despite the coronavirus disease pandemic. The middle-aged group (45-64 years old) had a higher rate of mortality than other age groups, and the highest proportion of individuals on Medical Aid. CONCLUSION: It is necessary to plan age- and gender-specific suicide prevention programs that focus on improving the limited public mental health resources for the vulnerable populations.

Whole Genome Sequencing of SARS-CoV-2 in Cats and Dogs in South Korea in 2021.

SARS-CoV-2 infections have caused unprecedented damage worldwide by affecting humans and various animals. The first reported animal infection was observed in a pet dog in Hong Kong in March 2020. 36 countries reported 692 SARS-CoV-2 infections in 25 different animal species by 31 August 2022. Most outbreaks were caused by contact with SARS-CoV-2 infected humans. In South Korea, the first SARS-CoV-2 infection in an animal was reported in a cat in February 2021. As of 31 December 2021, 74 dogs and 42 cats have been confirmed to have SARS-CoV-2 in South Korea. Here, we identified various SARS-CoV-2 genomic lineages in SARS-CoV-2 confirmed cats and dogs. Among the 40 animal samples sequenced for lineage identification, a total of eight Pango lineages (B.1.1.7 (Alpha variant), B.1.429 (Epsilon variant), B.1.470, B.1.497, B.1.619.1, B.1.620, AY.69 (Delta variant), and AY.122.5 (Delta variant)) were identified. The dominant lineages were AY.69 (Delta variant; 37.5%), B.1.497 (35.0%), and B.1.619.1 (12.5%). This study provides the first reported cases of six lineages (B.1.470, B.1.497, B.1.620, B.1.619.1, AY.69 (Delta variant)), and AY.122.5 (Delta variant) in cats and dogs. Our results emphasize the importance of monitoring SARS-CoV-2 in pets because they are dynamic hosts of variant Pango lineages of SARS-CoV-2.

Changing Features of Liver Injury in COVID-19 Patients: Impact of Infection with the SARS-CoV-2 Delta (B.1.617.2) Variants.

BACKGROUND: There is growing evidence that abnormal liver function tests (LFTs) are common in patients with coronavirus disease 2019 (COVID-19). However, it is not known whether viral involvement in the liver differs according to the strain. We investigated the impact on liver injury in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta (B.1.617.2) variants. MATERIALS AND METHODS: We conducted a single-center, retrospective cohort study, including 372 patients admitted during the pre-Delta period (PDP: between February 1 and November 30, 2020) and 137 patients admitted during the Delta period (DP: between August 1 and August 31, 2021). Initial liver injury was defined as alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels ≥3 × the upper limit of normal (ULN) or alkaline phosphatase (ALP) or total bilirubin ≥2 × the ULN within 3 days from admission. RESULTS: Of 509 patients with COVID-19 included in our study, 38 (7.5%) patients had initial liver injury. The DP group had a significantly higher rate of initial liver injury than the PDP group (PDP: 5.9% vs. DP: 11.7%, P = 0.028). The DP group (adjusted odds ratio [aOR]: 2.737, 95% confidence interval [CI]: 1.322 - 5.666) was independently associated with initial liver injury. During hospitalization, 160 (31.4%) patients had severe COVID-19. The DP group and initial liver injury had higher odds of progressing to severe COVID-19 (aOR: 2.664, 95% CI: 1.526 - 4.648, and aOR: 4.409, 95% CI: 1.816 - 10.707, respectively). The mediation analysis suggested that initial liver injury mediates the relationship between SARS-CoV-2 Delta variant infection and severe COVID-19 (unstandardized beta coefficient = 0.980, Standard error = 0.284, P = 0.001). CONCLUSION: Initial liver injury is more common in COVID-19 patients with Delta variants. Also, Delta variants and initial liver injury are associated with poor clinical outcomes.

Factors Related to Anxiety and Depression Among Adolescents During COVID-19: A Web-Based Cross-Sectional Survey.

BACKGROUND: The coronavirus disease 2019 (COVID-19) outbreak and subsequent disease-containment measures (such as school closures) significantly affected the lives of adolescents. We evaluated the mental-health status and factors associated with anxiety and depression among South Korean adolescents. METHODS: A nationwide online survey was conducted to evaluate the mental-health status of South Korean adolescents during the COVID-19 pandemic. In total, 570 adolescents aged 13-18 years were surveyed between May 27 and June 11, 2021. The participants completed the Generalized Anxiety Disorder Scale (GAD-7) and Patient Health Questionnaire (PHQ-9) to determine anxiety and depression symptoms, respectively. Stepwise logistic regression models were constructed to determine factors related to anxiety and depression. RESULTS: Among the study participants, 11.2% and 14.2% had anxiety and depression, respectively. The results suggested that several factors, such as the experience of COVID-19 infection and quarantine of oneself, a family member or an acquaintance, physical and mental health problems, and fear of one's local community being discriminated against as a COVID-19 area were related to anxiety and depression. CONCLUSION: The present study identified COVID-19-related factors associated with anxiety and depression among adolescents, and provides insights regarding potential interventions to improve the mental health of adolescents. To promote the mental health of adolescents during the COVID-19 pandemic, special attention should be paid to individuals with physical or mental-health problems, and efforts should be made to reduce the negative social and emotional impacts of infection-control measures.

The association between greenness exposure and COVID-19 incidence in South Korea: An ecological study.

BACKGROUND: The rapid spread of COVID-19 has caused an emergency situation worldwide. Investigating the association between environmental characteristics and COVID-19 incidence can be of the occurrence and transmission. The objective of this study was to evaluate the association between greenness exposure and COVID-19 cases at the district levels in South Korea. We also explored this association by considering several environmental indicators. METHODS: District-level data from across South Korea were used to model the cumulative count of COVID-19 cases per 100,000 persons between January 20, 2020, and February 25, 2021. Greenness exposure data were derived from the Environmental Geographic Information Service of the Korean Ministry of Environment. A negative binomial mixed model evaluated the association between greenness exposure and COVID-19 incidence rate at the district level. Furthermore, we assessed this association between demographic, socioeconomic, environmental statuses, and COVID-19 incidence. RESULTS: Data from 239 of 250 districts (95.6%) were included in the analyses, resulting in 127.89 COVID-19 cases per 100,000 persons between January 20, 2020 and February 25, 2021. Several demographic and socioeconomic variables, districts with a higher rate of natural greenness exposure, were significantly associated with lower COVID-19 incidence rates (incidence rate ratio (IRR), 0.70; 95% confidence interval (CI), 0.54-0.90; P-value = 0.008) after adjusting covariates, but no evidence for the association between built greenness and COVID-19 incidence rates was found. CONCLUSION: In this ecological study of South Korea, we found that higher rates of exposure to natural greenness were associated with lower rates of COVID-19 cases.

Booster BNT162b2 COVID-19 Vaccination Increases Neutralizing Antibody Titers Against the SARS-CoV-2 Omicron Variant in Both Young and Elderly Adults.

Concerns about the effectiveness of current vaccines against the rapidly spreading severe acute respiratory syndrome-coronavirus-2 omicron (B.1.1.529) variant are increasing. This study aimed to assess neutralizing antibody activity against the wild-type (BetaCoV/Korea/KCDC03/2020), delta, and omicron variants after full primary and booster vaccinations with BNT162b2. A plaque reduction neutralization test was employed to determine 50% neutralizing dilution (ND50) titers in serum samples. ND50 titers against the omicron variant (median [interquartile range], 5.3 [< 5.0-12.7]) after full primary vaccination were lower than those against the wild-type (144.8 [44.7-294.0]) and delta (24.3 [14.3-81.1]) variants. Furthermore, 19/30 participants (63.3%) displayed lower ND50 titers than the detection threshold (< 10.0) against omicron after full primary vaccination. However, the booster vaccine significantly increased ND50 titers against BetaCoV/Korea/KCDC03/2020, delta, and omicron, although titers against omicron remained lower than those against the other variants (P < 0.001). Our study suggests that booster vaccination with BNT162b2 significantly increases humoral immunity against the omicron variant.

Comparison of Complications after Coronavirus Disease and Seasonal Influenza, South Korea.

We conducted a retrospective cohort study using claims data to determine the number and types of complications from coronavirus disease (COVID-19) that patients experience and which patients are more vulnerable to those complications compared with complications in patients with influenza. Among the cohort, 19.6% of COVID-19 patients and 28.5% of influenza patients had >1 new complication. In most complications, COVID-19 patients had lower or similar relative risk compared with influenza patients; exceptions were hair loss, heart failure, mood disorder, and dementia. Young to middle-aged adult COVID-19 patients and patients in COVID-19 hotspots had a higher risk for complications. Overall, COVID-19 patients had fewer complications than influenza patients, but caution is necessary in high-risk groups. If the fatality rate for COVID-19 is reduced through vaccination, management strategies for this disease could be adapted, similar to those for influenza management, such as easing restrictions on economic activity or requirements for close-contact isolation.

Clinical Characteristics of 40 Patients Infected With the SARS-CoV-2 Omicron Variant in Korea.

Since severe acute respiratory syndrome-coronavirus-2 variant B.1.1.529 (omicron) was first reported to the World Health Organization on November 24, 2021, the cases of the omicron variant have been detected in more than 90 countries over the last month. We investigated the clinical and epidemiological characteristics of the first 40 patients with the omicron variant who had been isolated at the National Medical Center in South Korea during December 4-17, 2021. The median age of the patients was 39.5 years. Twenty-two patients (55%) were women. Seventeen patients (42.5%) were fully vaccinated, and none were reinfected with the omicron. Eighteen (45%) had recent international travel history. Half of the patients (19, 47.5%) were asymptomatic, while the others had mild symptoms. Six patients (15%) showed lung infiltrations on chest image; however, none required supplemental oxygen. These mild clinical features are consistent with recent case reports on the omicron variant from other countries.

Predictors of the Development of Mental Disorders in Hospitalized COVID-19 Patients without Previous Psychiatric History: A Single-Center Retrospective Study in South Korea.

The objective of this study was to investigate the predictors for new-onset mental disorders among patients with mild to moderate COVID-19 illness during hospitalization. A retrospective cohort study was performed in patients with confirmed COVID-19 admitted to a nationally designated hospital between 1 February and 30 June 2020. Demographic, clinical, psychological assessments, and psychiatric outcomes were obtained from electronic medical record review. Multivariate logistic regression analysis was used to identify predictors of new-onset mental disorders. Among 185 patients, 130 had no history of mental disorders or cognitive impairment at the time of admission. Of 130 patients, 29 (22.3%) were newly diagnosed with mental disorders during hospitalization. The following factors were significantly associated with an increased risk of a psychiatric diagnosis: Charlson comorbidity index core ≥1 (adjusted odds ratio (aOR) = 5.115, 95% confidence interval (CI): 1.737-15.058), length of stay (aOR per 1-day increase = 1.067, 95% CI: 1.035-1.100), and self-reported depressive symptoms at the time of admission (aOR = 5.357, 95% CI: 1.745-16.444). The predictive accuracy of combining these risk factors was relatively high (area under curve = 0.851, 95% CI: 0.778-0.923). These potential risk factors could help to predict the new-onset mental disorder among hospitalized patients with COVID-19.

The Use of Personal Protective Equipment among Frontline Nurses in a Nationally Designated COVID-19 Hospital during the Pandemic.

BACKGROUND: The appropriate use of personal protective equipment (PPE) can significantly reduce the risk of infection associated with caring for patients. This study aimed to investigate the knowledge, awareness, and behaviors related to the PPE usage among frontline nurses in a nationally designated coronavirus disease 2019 (COVID-19) hospital during the COVID-19 pandemic. MATERIALS AND METHODS: The study was performed in two phases: (1) a questionnaire survey to assess the knowledge, awareness, and behaviors related to PPE use, and (2) in-depth personal interviews to elaborate the survey findings. The questionnaires were distributed to all 121 registered nurses in three isolation wards and an intensive care unit which dedicated for patients with COVID-19 and 102 nurses completed survey (84.3% response rate). In-depth interviews were conducted with a total of 7 nurses. RESULTS: Among the survey participant, 100% stated that they knew how to protect themselves while providing nursing care and 93.1% stated that they knew the recommended PPE by task. Most survey participant mainly wore gloves, face shield, N95 or equivalent respirator, and a long-sleeved gown, but one-third of the participants sometimes used coveralls instead of long-sleeved gown. In-depth interviews, the importance of timely updated and specific guidelines for selecting the appropriate type of PPE was highlighted. The adequate supply of PPE, convenience at work, and the role of responsible leadership mainly determined behaviors related to the PPE. CONCLUSION: As new information on COVID-19 continues to emerge, the up-to-date and specific PPE guideline with evidence should be prepared. The spread of accurate information, the role of accountable leadership, and the active communication under positive organizational culture are important for the proper use of PPE.

Impact of the COVID-19 Outbreak on Emergency Care Utilization in Patients with Acute Myocardial Infarction: a Nationwide Population-based Study.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has impacted various aspects of daily living and has influenced the life of every individual in a unique way. Acute myocardial infarction (AMI) is associated with high morbidity and mortality; thus, timely treatment is crucial to prevent poor prognosis. Therefore, an immediate emergency department (ED) visit is required; however, no domestic studies have reported the effect of COVID-19 on ED visits by patients with AMI. Therefore, this study aimed to assess the changes in the pattern of ED visits by patients with AMI by comparing visits during the COVID-19 outbreak period to those during two control periods. METHODS: This nationwide, retrospective study used registry data of the National Emergency Department Information System. The 'outbreak period' was defined as the period between February 21, 2020 and April 1, 2020, while the 'control period' was defined as the same time period in the preceding two years (2018 and 2019). The primary outcome of our study was the number of patients admitted to the ED owing to AMI during the outbreak and control periods. Secondary outcomes were time from symptom onset to ED visit, length of ED stay, and 30-day mortality following admission. RESULTS: During the outbreak period, 401,378 patients visited the ED; this number was lower than that during the control periods (2018: 577,548; 2019: 598,514). The number of patients with AMI visiting the ED was lower during the outbreak period (2,221) than during 2018 (2,437) and 2019 (2,591). CONCLUSION: The COVID-19 pandemic has caused a reduction in ED visits by patients with AMI. We assume that this could likely be caused by misinterpretation of AMI symptoms as symptoms of respiratory infection, fear of contracting severe acute respiratory syndrome coronavirus 2, and restrictions in accessing emergency medical care owing to overburdened healthcare facilities. This study sheds light on the fact that healthcare and emergency medical staff members must work towards eliminating hurdles due to this pandemic for patients to receive timely emergency care, which in turn will help curb the growing burden of mortality.

Clinical Course and Outcomes of 3,060 Patients with Coronavirus Disease 2019 in Korea, January-May 2020.

BACKGROUND: The fatality rate of patients with coronavirus disease 2019 (COVID-19) varies among countries owing to demographics, patient comorbidities, surge capacity of healthcare systems, and the quality of medical care. We assessed the clinical outcomes of patients with COVID-19 during the first wave of the epidemic in Korea. METHODS: Using a modified World Health Organization clinical record form, we obtained clinical data for 3,060 patients with COVID-19 treated at 55 hospitals in Korea. Disease severity scores were defined as: 1) no limitation of daily activities; 2) limitation of daily activities but no need for supplemental oxygen; 3) supplemental oxygen via nasal cannula; 4) supplemental oxygen via facial mask; 5) non-invasive mechanical ventilation; 6) invasive mechanical ventilation; 7) multi-organ failure or extracorporeal membrane oxygenation therapy; and 8) death. Recovery was defined as a severity score of 1 or 2, or discharge and release from isolation. RESULTS: The median age of the patients was 43 years of age; 43.6% were male. The median time from illness onset to admission was 5 days. Of the patients with a disease severity score of 3-4 on admission, 65 (71.5%) of the 91 patients recovered, and 7 (7.7%) died due to illness by day 28. Of the patients with disease severity scores of 5-7, 7 (19.5%) of the 36 patients recovered, and 8 (22.2%) died due to illness by day 28. None of the 1,324 patients who were < 50 years of age died; in contrast, the fatality rate due to illness by day 28 was 0.5% (2/375), 0.9% (2/215), 5.8% (6/104), and 14.0% (7/50) for the patients aged 50-59, 60-69, 70-79, and ≥ 80 years of age, respectively. CONCLUSION: In Korea, almost all patients of < 50 years of age with COVID-19 recovered without supplemental oxygen. In patients of ≥ 50 years of age, the fatality rate increased with age, reaching 14% in patients of ≥ 80 years of age.