Evolution of Responses to COVID-19 and Epidemiological Characteristics in South Korea

Uncovering COVID-19 transmission tree: identifying traced and untraced infections in an infection network

Introduction

This paper presents a comprehensive analysis of COVID-19 transmission dynamics using an infection network derived from epidemiological data in South Korea, covering the period from January 3, 2020, to July 11, 2021. The network illustrates infector-infectee relationships and provides invaluable insights for managing and mitigating the spread of the disease. However, significant missing data hinder conventional analysis of such networks from epidemiological surveillance.

Methods

To address this challenge, this article suggests a novel approach for categorizing individuals into four distinct groups, based on the classification of their infector or infectee status as either traced or untraced cases among all confirmed cases. The study analyzes the changes in the infection networks among untraced and traced cases across five distinct periods.

Results

The four types of cases emphasize the impact of various factors, such as the implementation of public health strategies and the emergence of novel COVID-19 variants, which contribute to the propagation of COVID-19 transmission. One of the key findings is the identification of notable transmission patterns in specific age groups, particularly in those aged 20-29, 40-69, and 0-9, based on the four type classifications. Furthermore, we develop a novel real-time indicator to assess the potential for infectious disease transmission more effectively. By analyzing the lengths of connected components, this indicator facilitates improved predictions and enables policymakers to proactively respond, thereby helping to mitigate the effects of the pandemic on global communities.

Conclusion

This study offers a novel approach to categorizing COVID-19 cases, provides insights into transmission patterns, and introduces a real-time indicator for better assessment and management of the disease transmission, thereby supporting more effective public health interventions.

Core health system measures response to COVID-19 among East Asian countries

Objective

The purpose of this study is to summarize the health system response to COVID-19 in four East Asian countries, analyze the effectiveness of their health system response, and provide lessons for other countries to control the epidemic and optimize their health system response.

Methods

This study investigated and summarized COVID-19 data and health system response in four East Asian countries, China, Japan, Mongolia, and South Korea from national governments and ministries of health, WHO country offices, and official websites of international organizations, to assess the effectiveness of health system measures.

Result

As of June 30, 2022, all four countries are in a declining portion of COVID-19. China has two waves, and new cases increased slowly, with the total cases per million remaining within 4, indicating a low level. Japan has experienced six waves, with case growth at an all-time high, total cases per million of 250.994. Mongolia started the epidemic later, but also experienced four waves, with total cases per million of 632.658, the highest of the four countries. South Korea has seen an increasing number of new cases per wave, with a total case per million of 473.759.

Conclusion

In containment strategies adopted by China and Mongolia, and mitigation strategies adopted by Japan and South Korea, health systems have played important roles in COVID-19 prevention and control. While promoting vaccination, countries should pay attention to non-pharmaceutical health system measures, as evidenced by: focusing on public information campaigns to lead public minds; strengthening detection capabilities for early detection and identification; using technical ways to participate in contact tracing, and promoting precise judging isolation.

The mortality of patients with sepsis increases in the first month of a new academic year

OBJECTIVE

Many studies have examined the July effect. However, little is known about the July effect in sepsis. We hypothesized that the July effect would result in worse outcomes for patients with sepsis.

METHODS

Data from patients with sepsis, collected prospectively between January 2018 and December 2021, were analyzed. In Korea, the new academic year starts on March 1, so the "July effect" appears in March. The primary outcome was 30-day mortality. Secondary outcomes included adherence to the Surviving Sepsis Campaign bundle. Outcomes in March were compared to other months. A multivariate Cox proportional hazard regression was performed to adjust for confounders.

RESULTS

We included 843 patients. There were no significant differences in sepsis severity. The 30-day mortality in March was higher (49.0% vs. 28.5%, P<0.001). However, there was no difference in bundle adherence in March (42.2% vs. 48.0%, P=0.264). The multivariate Cox proportional hazard regression showed that the July effect was associated with 30-day mortality in patients with sepsis (adjusted hazard ratio, 1.925; 95% confidence interval, 1.405-2.638; P<0.001).

CONCLUSION

The July effect was associated with 30-day mortality in patients with sepsis. However, bundle adherence did not differ. These.

RESULTS

suggest that the increase in mortality during the turnover period might be related to unmeasured in-hospital management. Intensive supervision and education of residents caring for patients with sepsis is needed in the beginning of training.

The elderly population are more vulnerable for the management of colorectal cancer during the COVID-19 pandemic: a nationwide, population-based study

BACKGROUND/AIMS

The impact of coronavirus disease 2019 (COVID-19) on the management of colorectal cancer (CRC) may worse in elderly population, as almost all COVID-19 deaths occurred in the elderly patients. This study aimed to evaluate the impact of COVID-19 on CRC management in the elderly population.

METHODS

The numbers of patients who underwent colonoscopy, who visited hospitals or operated for CRC in 2020 and 2021 (COVID-19 era) were compared with those in 2019, according to 3 age groups (≥70 years, 50-69 years, and ≤49 years), based on the nationwide, population-based database (2019-2021) in South Korea.

RESULTS

The annual volumes of colonoscopy and hospital visits for CRC in 2020 were more significantly declined in the old age group than in the young age group (both P<0.001). In addition, the annual volume of patients operated for CRC numerically more declined in old age group than in young age group. During the first surge of COVID-19 (March and April 2020), old age patients showed statistically significant declines for the monthly number of colonoscopies (-46.5% vs. -39.3%, P<0.001), hospital visits (-15.4% vs. -7.9%, P<0.001), CRC operations (-33.8% vs. -0.7%, P<0.05), and colonoscopic polypectomies (-41.8% vs. -38.0%, P<0.001) than young age patients, compared with those of same months in 2019.

CONCLUSIONS

Elderly population are more vulnerable for the management of CRC during the COVID-19 pandemic. Therefore, the elderly population are more carefully cared for in the management of CRC during the next pandemic.

Impact of the COVID-19 Pandemic on Esophagogastroduodenoscopy and Gastric Cancer Claims in South Korea: A Nationwide, Population-Based Study

PURPOSE

There has been little information about the impact of coronavirus disease 2019 (COVID-19) pandemic on esophagogastroduodenoscopy (EGD) and gastric cancer claims. This study aimed to measure the impact of COVID-19 pandemic on EGD and gastric cancer claims in South Korea.

MATERIALS AND METHODS

This nationwide, population-based study compared the claims data of EGD, gastric cancer, early gastric cancer (EGC), advanced gastric cancer (AGC) and gastric cancer operation in 2020 and 2021 (COVID-19 era) to those in 2019 (before COVID-19 pandemic).

RESULTS

The annual claims of EGD, gastric cancer, EGC, and AGC were reduced by 6.3%, 5.0%, 4.7%, and 3.6% in 2020 and by 2.2%, 1.0%, 0.6%, and 1.9% in 2021, respectively, compared to 2019. The amount of annual claims of gastric cancer operation was reduced by 8.8% in 2020, but increased by 0.9% in 2021, compared to those in 2019. The monthly claims of EGD, gastric cancer, EGC, AGC, and gastric cancer operation were mainly reduced in the first epidemic wave of COVID-19, but decreased in the 2nd to 4th epidemic wave. Compared to 2019, the monthly claim of EGD, gastric cancer, EGC, AGC, and gastric cancer operation were reduced by 28.8%, 14.3%, 18.1%, 9.2%, and 5.8% in March 2020 and by 17.2%, 10.8%, 10.3%, 7.2%, and 35.4% in April 2020, respectively.

CONCLUSION

Negative impact of the COVID-19 pandemic on EGD, gastric cancer, EGC, AGC, and gastric cancer operation was worst during the first surge of COVID-19, but decreased in the 2nd to 4th epidemic wave of the disease in 2020 and 2021.

Utilization of the Unlinked Case Proportion to Control COVID-19: A Focus on the Non-pharmaceutical Interventional Policies of the Korea and Japan

OBJECTIVES

Korea and Japan have managed the spread of coronavirus disease 2019 (COVID-19) using markedly different policies, referred to as the "3T" and "3C" strategies, respectively. This study examined these differences to assess the roles of active testing and contact tracing as non-pharmaceutical interventions (NPIs). We compared the proportion of unlinked cases (UCs) and test positivity rate (TPR) as indicators of tracing and testing capacities.

METHODS

We outlined the evolution of NPI policies and investigated temporal trends in their correlations with UCs, confirmed cases, and TPR prior to the Omicron peak. Spearman correlation coefficients were reported between the proportion of UCs, confirmed cases, and TPR. The Fisher r-to-z transformation was employed to examine the significance of differences between correlation coefficients.

RESULTS

The proportion of UCs was significantly correlated with confirmed cases (r=0.995, p<0.001) and TPR (r=0.659, p<0.001) in Korea and with confirmed cases (r=0.437, p<0.001) and TPR (r=0.429, p<0.001) in Japan. The Fisher r-to-z test revealed significant differences in correlation coefficients between the proportion of UCs and confirmed cases (z=16.07, p<0.001) and between the proportion of UCs and TPR (z=2.12, p=0.034) in Korea and Japan.

CONCLUSIONS

Higher UCs were associated with increases in confirmed cases and TPR, indicating the importance of combining testing and contact tracing in controlling COVID-19. The implementation of stricter policies led to stronger correlations between these indicators. The proportion of UCs and TPR effectively indicated the effectiveness of NPIs. If the proportion of UCs shows an upward trend, more testing and contact tracing may be required.

Improved time-varying reproduction numbers using the generation interval for COVID-19

Estimating key epidemiological parameters, such as incubation period, serial interval (SI), generation interval (GI) and latent period, is essential to quantify the transmissibility and effects of various interventions of COVID-19. These key parameters play a critical role in quantifying the basic reproduction number. With the hard work of epidemiological investigators in South Korea, estimating these key parameters has become possible based on infector-infectee surveillance data of COVID-19 between February 2020 and April 2021. Herein, the mean incubation period was estimated to be 4.9 days (95% CI: 4.2, 5.7) and the mean generation interval was estimated to be 4.3 days (95% CI: 4.2, 4.4). The mean serial interval was estimated to be 4.3, with a standard deviation of 4.2. It is also revealed that the proportion of presymptomatic transmission was ~57%, which indicates the potential risk of transmission before the disease onset. We compared the time-varying reproduction number based on GI and SI and found that the time-varying reproduction number based on GI may result in a larger estimation of Rt, which refers to the COVID-19 transmission potential around the rapid increase of cases. This highlights the importance of considering presymptomatic transmission and generation intervals when estimating the time-varying reproduction number.

Predicting adherence to COVID-19 preventive measures among South Korean adults aged 40 to 69 Years using the expanded health empowerment model

The public health environment in South Korea is advancing toward the late stages of the COVID-19 pandemic. However, there is limited knowledge about the extent of individuals' compliance with preventive measures during this transitional period and the potential predictors that determine such compliance behaviors. In this study, we employed the expanded health empowerment model to investigate factors associated with COVID-19 preventive behaviors among Korean adults in late 2022. Our theoretical framework integrates the knowledge-attitude-behavior model with the health belief model to conceptualize health empowerment underlying the formation of preventive behaviors. We collected data from 1100 Korean adults aged 40-69 years through an online survey conducted in October 2022. Participants responded to questions about their knowledge of COVID-19, attitudes towards the disease, adherence to preventive measures, infection history, and sociodemographic characteristics. Structural equation modeling was employed to assess the relationships between knowledge, attitudes, and preventive behaviors related to COVID-19. Results showed that attitudes toward the disease predict adherence to preventive behaviors. We also found that COVID-19 knowledge partially determined the attitudes toward the disease. However, COVID-19 knowledge was not directly associated with adherence to preventive behaviors. Additionally, the associations between knowledge, attitudes, and preventive behaviors did not differ between infected and never-infected individuals. Overall, this study finds empirical support for the expanded health empowerment model, which connects knowledge to preventive behaviors through positive attitudes toward the disease, while underscoring the limited role of infection history in this association. These findings can help policymakers understand individual responses to public health guidelines in the late pandemic era and develop policies to mitigate further transmission of COVID-19.

Heterogeneity is a key factor describing the initial outbreak of COVID-19

Assessing the transmission potential of emerging infectious diseases, such as COVID-19, is crucial for implementing prompt and effective intervention policies. The basic reproduction number is widely used to measure the severity of the early stages of disease outbreaks. The basic reproduction number of standard ordinary differential equation models is computed for homogeneous contact patterns; however, realistic contact patterns are far from homogeneous, specifically during the early stages of disease transmission. Heterogeneity of contact patterns can lead to superspreading events that show a significantly high level of heterogeneity in generating secondary infections. This is primarily due to the large variance in the contact patterns of complex human behaviours. Hence, in this work, we investigate the impacts of heterogeneity in contact patterns on the basic reproduction number by developing two distinct model frameworks: 1) an SEIR-Erlang ordinary differential equation model and 2) an SEIR stochastic agent-based model. Furthermore, we estimated the transmission probability of both models in the context of COVID-19 in South Korea. Our results highlighted the importance of heterogeneity in contact patterns and indicated that there should be more information than one quantity (the basic reproduction number as the mean quantity), such as a degree-specific basic reproduction number in the distributional sense when the contact pattern is highly heterogeneous.

Soluble ST2 as a Useful Biomarker for Predicting Clinical Outcomes in Hospitalized COVID-19 Patients

Soluble suppression of tumorigenesis-2 (sST2) is an emerging biomarker for sepsis as well as for heart failure. We investigated the prognostic utility of sST2 for predicting clinical outcomes in hospitalized coronavirus disease 2019 (COVID-19) patients. In a total of 52 hospitalized COVID-19 patients, sST2 levels were measured using the ichroma ST2 assay (Boditech Med Inc., Chuncheon-si, Gang-won-do, Republic of Korea). Clinical outcomes included intensive care unit (ICU) admission, ventilator use, extracorporeal membrane oxygenation (ECMO) use, and 30-day mortality. sST2 was analyzed according to clinical outcomes. sST2, sequential organ failure assessment (SOFA) score, critical disease, and 4C mortality score were compared using the receiver operating characteristic (ROC) curve and Kaplan−Meier methods for clinical outcomes. The sST2 level differed significantly according to ICU admission, ventilator use, ECMO use, and 30-day mortality (all p < 0.05). On ROC curve analysis, sST2 predicted ICU admission, ventilator use, ECMO use, and 30-day mortality comparable to SOFA score but significantly better than critical disease. sST2 predicted ICU admission, ventilator use, and ECMO use significantly better than the 4C mortality score. On Kaplan−Meier survival analysis, hazard ratios (95% confidence interval) were 8.4 (2.7−26.8) for sST2, 14.8 (3.0−71.7) for SOFA score, 1.8 (0.5−6.5) for critical disease, and 11.7 (3.4−40.1) for 4C mortality score. This study demonstrated that sST2 could be a useful biomarker to predict ICU admission, ventilator use, ECMO use, and 30-day mortality in hospitalized COVID-19 patients. sST2 may be implemented as a prognostic COVID-19 biomarker in clinical practice.

Clustering and link prediction for mesoscopic COVID-19 transmission networks in Republic of Korea

We analyze the dataset of confirmed cases of severe acute respiratory syndrome coronavirus 2 (COVID-19) in the Republic of Korea, which contains transmission information on who infected whom as well as temporal information regarding when the infection possibly occurred. We derive time series of mesoscopic transmission networks using the location and age of each individual in the dataset to see how the structure of these networks changes over time in terms of clustering and link prediction. We find that the networks are clustered to a large extent, while those without weak links could be seen as having a tree structure. It is also found that triad-based link predictability using the network structure could be improved when combined with additional information on mobility and age-stratified contact patterns. Abundant triangles in the networks can help us better understand mixing patterns of people with different locations and age groups, hence the spreading dynamics of infectious disease.

Endotracheal Intubation Using C-MAC Video Laryngoscope vs. Direct Laryngoscope While Wearing Personal Protective Equipment

This study sought to determine whether the C-MAC video laryngoscope (VL) performed better than a direct laryngoscope (DL) when attempting endotracheal intubation (ETI) in the emergency department (ED) while wearing personal protective equipment (PPE). This was a retrospective single-center observational study conducted in an academic ED between February 2020 and March 2022. All emergency medical personnel who participated in any ETI procedure were required to wear PPE. The patients were divided into the C-MAC VL group and the DL group based on the device used during the first ETI attempt. The primary outcome measure was the first-pass success (FPS) rate. A multiple logistic regression was used to determine the factors associated with FPS. Of the 756 eligible patients, 650 were assigned to the C-MAC group and 106 to the DL group. The overall FPS rate was 83.5% (n = 631/756). The C-MAC group had a significantly higher FPS rate than the DL group (85.7% vs. 69.8%, p < 0.001). In the multivariable logistic regression analysis, C-MAC use was significantly associated with an increased FPS rate (adjusted odds ratio, 2.86; 95% confidence interval, 1.69−4.08; p < 0.001). In this study, we found that the FPS rate of ETI was significantly higher when the C-MAC VL was used than when a DL was used by emergency physicians constrained by cumbersome PPE.