key: cord-0703304-jmk7i3s8 authors: Ahn, Jong Gyun title: Epidemiological changes in infectious diseases during the coronavirus disease 2019 pandemic in Korea: a systematic review date: 2021-11-30 journal: Clin Exp Pediatr DOI: 10.3345/cep.2021.01515 sha: 2d97b28d01e1006226efc919de8e2c13c5d598bc doc_id: 703304 cord_uid: jmk7i3s8 In the era of the coronavirus disease 2019 (COVID-19) pandemic, countries worldwide have implemented several nonpharmaceutical interventions (NPIs) to contain its spread before vaccines and treatments were developed. NPIs included social distancing, mask wearing, intensive contact tracing and isolation, and sanitization. In addition to their effectiveness at preventing the rapid spread of COVID-19, NPIs have caused secondary changes in the epidemiology of other infectious diseases. In Korea, various NPI stages have been implemented since the first confirmed case of COVID-19 on January 20, 2020. This review, based on a PubMed database search, shows the impact of NPIs on several infectious diseases other than severe acute respiratory syndrome coronavirus 2 in the COVID-19 pandemic era in Korea. Since the declaration of the coronavirus disease 2019 (COVID- 19) pandemic, many countries worldwide, including Korea, have implemented strong quarantine measures based on nonpharmaceutical interventions (NPIs) to suppress its spread. 1) NPIs, also called community mitigation strategies, are a set of measures separate from vaccination and medication that help individuals and communities slow the spread of an epidemic. NPIs include social distancing, mask wearing, intensive contact tracing and isolation, and sanitization. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, is a new virus to which humans do not have immunity. Thus, SARS-CoV-2 spread rapidly worldwide and caused a global pandemic. NPIs are one of the best ways to control such pandemics when a vaccine is not yet available. [2] [3] [4] On February 23, 2020, the Korean government raised the infectious disease crisis level to severe and operated the Central Disaster and Safety Countermeasures Headquarters to focus on pan-government quarantine. Three T (testing, tracking, treatment) strategies and social distancing adjustments have been made to continuously suppress the incidence of disease and minimize damage in the event of a large-scale outbreak. As of September 2021, the Central Disease Control Headquarters calculates the infection reproduction number (R) to analyze and predict the spread of COVID-19 and applied the quarantine policy in 4 stages according to the R value. 5) Since the main transmission routes of SARS-CoV-2 are droplet transmission and direct contact, the NPI policy implemented to suppress its transmission may affect the epidemiologic characteristics of other respiratory and nonrespiratory diseases that are prevalent in the community. In the COVID-19 pandemic, it is important to understand trends in current infectious disease epidemiology and predict the postpandemic epidemiology of infectious diseases. This is because the pediatric population is susceptible to various infectious diseases, and in the current epidemiological situation, a temporary reduction of any infectious disease may lead to a large-scale future outbreak due to the accumulation of susceptible persons. Therefore, this review discusses epidemiological changes in 6, 7, 9, 11, 12, 15) analyzed some of the viruses. Of those 6 studies, 4 were of IFV. 6, 9, 11, 12) The results differed among studies due to differences in analytical methods and study periods, but all showed that respiratory virus infections after the start of the COVID-19 pandemic had decreasing trends. This is thought to be due to the effectiveness of NPIs used to control COVID-19 infections. However, 2 studies reported that nonenveloped viruses (ADV, infectious diseases during the COVID-19 pandemic in Korea based on searches of the PubMed database. In particular, this review focuses on epidemiologic changes in respiratory and nonrespiratory diseases due to NPIs. PubMed was searched by combining the terms (COVID-19 pandemic, COVID-19, coronavirus disease 2019, SARS-CoV-2, severe acute respiratory syndrome coronavirus 2, Wuhan coronavirus) and (nonpharmaceutical, social distancing, social distance, cohort grouping, community containment, isolation strategy, isolation, physical contact, physical distancing, quarantine, quarantining, banning, distancing, lockdown, stay at home, contact, mask) and (Korea) to identify studies that reported on epidemiological changes in infectious diseases during the COVID-19 pandemic in Korea. The search was performed on September 24, 2021. The search revealed 699 results; after the removal of duplicates and exclusion of studies based on title and abstract screening, 15 relevant studies were subjected to full-text review. Of them, one was excluded because it was irrelevant to the main topic. Therefore, 14 articles were included in this systematic review (Fig. 1) . A summary of the included articles is outlined in Table 1 . [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] Changes in respiratory disease epidemiology 1 There were a total of 10 studies on respiratory viruses. [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] Among them, 9 studies were analyzed using data from the surveillance system operated by the Korea Disease Control and HRV, and HBoV) were continuously detected even after the introduction of NPIs. Why the effectiveness of NPIs differed between respiratory viruses remains unclear, but it may be due to the unique characteristics of the specific viruses, subtle differences in respiratory transmission modes and viral shedding durations, and differences in resistance against environmental conditions. 8, 14, [20] [21] [22] In Korea, the mandatory surveillance of group 1-3 infectious diseases is implemented according to communicable disease types. Two studies 7,15) compared the monthly incidence before versus after NPIs for infectious diseases with respiratory transmission monitored by the KDCA. Both studies included varicella, mumps, invasive pneumococcal disease, and pertussis. In one of the studies, scarlet fever was further analyzed. 7) The monthly incidence of notifiable respiratory diseases during the NPI period decreased remarkably compared to the pre-NPI period. The largest reductions were observed for mumps and chicken pox. One study 6) compared hospitalization rates before and after NPI for COPD and asthma, which are chronic lung diseases, in addition to pneumonia and influenza. Hospitalization data were collected from the NHIS database. The study results reported that hospitalizations for COPD, asthma, and respiratory infections such as pneumonia and influenza decreased during the NPI era. In this study, the incidence of hospitalization for other acute and chronic diseases, such as diabetic ketoacidosis or hyperosmolar hyperglycemic state, intracranial hemorrhage, myo cardial infarction, and cancer, did not decrease after NPI, which demonstrated that these findings were not attributable to changes in healthcare utilization caused by the COVID-19 pandemic. Changes in nonrespiratory disease epidemiology 1 Two studies 16, 17) analyzed gastrointestinal infections using open data provided by the KDCA. Common analytical subjects of the 2 studies included norovirus and rotavirus for gastrointestinal viruses and Campylobacter spp., Clostridium perfringens, and nontyphoidal Salmonella for gastrointestinal bacteria. In one study, 3 enteric viruses (sapovirus, astrovirus, and enteric ADV) and 2 enteric bacteria (Staphylococcus aureus and enteropathogenic Escherichia coli) were further analyzed. 16) In both studies, the incidence of gastrointestinal viral infection significantly decreased after the introduction of NPI, whereas the incidence of gastrointestinal bacterial infections was not significantly reduced. This is thought to be because, in the case of the former, transmission occurs mainly by direct contact infec-tion, whereas in the case of the latter, transmission is food-borne. Kawasaki disease (KD) is an acute febrile vasculitis of childhood with the complication of coronary artery lesions. 23) The etiology of KD remains unknown, although its symptoms are thought to be related to an excessive immune system reaction triggered by an infectious agent in patients with genetic susceptibility. 24) Many observational epidemiologic studies have provided evidence of a link between KD and infection. They include clinical similarity to infectious disease in children, geographical and epidemic temporal clusters, seasonal trends, a strong relationship between KD and infection surveillance, and unusual recurrence. 25) However, no single pathogen has been identified to date. Two studies 18, 19) analyzed the incidence of KD before and after NPI in Korea using the NHIS claims database. One study 19) analyzed the overall KD incidence rate, while another 18) analyzed the KD-related hospitalization rate. The incidence of KD and the KD-related hospitalization rate decreased significantly after the introduction of NPIs. A decrease in KD after NPI has also been reported in the United States, Japan, and Singapore. 26) These findings emphasize the impact of extrinsic triggers such as common pediatric infections related to NPIs on the occurrence of KD. Two studies 7, 15) analyzed notifiable nonrespiratory infections. Both studies included hepatitis A. Hepatitis B was further analyzed in one study, 15) while hepatitis C and carbapenemresistant Enterobacterales were further investigated in another study. 7) Although the surge in hepatitis A observed in 2019 resulted in a relatively subtle decrease in hepatitis A during the NPI period, the observed cumulative incidence of hepatitis A was within the 95% confidence interval (CI) of the predicted value. The observed incidence of hepatitis C and carbapenem-resistant Enterobacterales during the NPI period remained within the 95% CIs of model predictions. There was also no change in the incidence of hepatitis B during the NPI period versus the pre-NPI period (2015-2019). NPIs launched to contain the spread of COVID-19 have had a major impact on the epidemiology of various infectious diseases in Korea. In particular, respiratory diseases and gastrointestinal viral diseases with respiratory transmission and direct contact transmission, the main transmission modes of SARS-CoV-2, were significantly reduced during the NPI period. In addition, the decrease in KD after the introduction of NPI, which was considered a causative factor of these infectious diseases, is an unintended result. If the policy of responding to COVID-19 changes due to the www.e-cep.org https://doi.org/10.3345/cep.2021.01515 171 introduction of vaccines and the development of therapeutic agents in the future and Korea transitions to an era "with corona," it is possible that infectious diseases that were reduced during the NPI period will re-emerge. In particular, one or more may appear in the form of an explosive epidemic in groups, including those of children who are susceptible to these infectious diseases. Therefore, it is very important to continuously monitor the epidemiology of these infectious diseases, predict the outbreak of an epidemic, and establish appropriate management policies. In addition, the study of these epidemiological changes may provide clues to the study of the etiology of various immune diseases induced by infectious diseases that occur as unintended consequences. Future research is needed on the immunological pathogenesis of KD and its relationship to infectious diseases. Conflicts of interest: No potential conflict of interest relevant to this article was reported. Funding: This study was supported by a faculty research grant of Yonsei University College of Medicine (6-2021-0145). Public health interventions for COVID-19: emerging evidence and implications for an evolving public health crisis Physical distancing, face masks, and eye protection to prevent person-toperson transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis Nonpharmaceutical measures for pandemic influenza in nonhealthcare settings-social distancing measures Estimating the effects of non-pharmaceutical interventions on COVID-19 in Europe COVID-19), Republic of Korea Korea Disease Control and Prevention Agency Decrease in hospital admissions for respiratory diseases during the COVID-19 pandemic: a nationwide claims study Impact of nonpharmaceutical interventions on the incidence of respiratory infections during the coronavirus disease 2019 (COVID-19) outbreak in Korea: a nationwide surveillance study Impact of coronavirus disease 2019 on respiratory surveillance and explanation of high detection rate of human rhinovirus during the pandemic in the Republic of Korea Respiratory syncytial virus and influenza epidemics disappearance in Korea during the 2020-2021 season of COVID-19 Impact of social distancing on the spread of common respiratory viruses during the coronavirus disease outbreak Impact of public health interventions on seasonal influenza activity during the COVID-19 outbreak in Korea Social distancing against COVID-19: implication for the control of influenza Changes in respiratory virus infection trends during the COVID-19 pandemic in South Korea: the effectiveness of public health measures Shifting patterns of respiratory virus activity following social distancing measures for COVID-19 in South Korea Impact of social distancing on incidence of vaccine-preventable diseases, South Korea Changes in the occurrence of Gastrointestinal Infections after COVID-19 in Korea Trend of gastrointestinal infections following nonpharmaceutical interventions, South Korea, 2020 Impact of social distancing on Kawasaki disease-associated hospitalization, South Korea Reduction in Kawasaki disease after nonpharmaceutical interventions in the COVID-19 era: a nationwide observational study in Korea Transmissibility and transmission of respiratory viruses Sanitizing agents for virus inactivation and disinfection. View (Beijing) Prolonged shedding of rhinovirus and re-infection in adults with respiratory tract illness Diagnosis, treatment, and long-term management of Kawasaki disease: a scientific statement for health professionals from the American Heart Association HMGB1 gene polymorphism is associated with coronary artery lesions and intravenous immunoglobulin resistance in Kawasaki disease Kawasaki disease An unintended consequence of pandemic control measures: fewer cases of Kawasaki disease How to cite this article: Ahn JG. Epidemiological changes in infectious diseases during the coronavirus disease 2019 pandemic in Korea: a systematic review