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.

Kawasaki disease (KD) is an acute febrile systemic vasculitis of early childhood with a predilection for the coronary arteries. Since the recent reports from the North America and European countries on Kawasaki-like disease or multisystem inflammatory syndrome in children (MIS-C) possible association with coronavirus disease-19 (COVID-19), 1,2 we explored whether this has been observed in Korean children. The incidence of KD in Korea is estimated to 217.2 per 100,000 children less than 5 years old, 10-30 fold higher than that of KD in North America and Europe. 3 The first patient with COVID-19 in Korea was identified on January 20, 2020, the first pediatric patients was identified on February 19, and the outbreak surge occurred at the end of February. 4 As of May 18, 2020, the number of pediatric cases (≤ 19 years) confirmed with positive severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) polymerase chain reaction (PCR) result was 768 out of 11,065 (6.9%) in the nation and among those, no case of Kawasaki-like clinical manifestations has been documented. 5 In addition, the number of patients with KD among the total new in-patients were searched in two tertiary referral centers in Seoul, Korea during each three months (February to April) from 2015 to 2020 (Fig. 1). A total of 429 children were diagnosed as KD among 14,714 new in-patients during the period. On average, more than 90% of the KD patients were from 0-5 year-age group. For a fair comparison, the proportion of KD patients hospitalized in these two hospitals out of all KD patients in the nation per year was examined. The total numbers of KD patients in the nation per year were retrieved from the Health Insurance Review and Assessment Service website, and proportions were calculated. 6 These proportions were similar with a range of 1.0% to 1.4% during each three months (February to April) from 2015 to 2019. There was no significant increase in KD-related hospitalization. The numbers of children with KD per 100 new in-patients were 3.5 in 2015, 3.2 in 2016, 3.0 in 2017, 2.9 in 2018, and 2.2 in 2019, and 2.6 in 2020. Despite 50 years of search for viral causality, the etiology of KD remains unknown. For example, coronavirus NL63, 229E and even bocavirus have been suggested for the association with KD but failed to clarify the definite association. 7,8 Epidemiologic reports on a sudden rise in MIS-C or Kawasaki-like disease, mainly in older children, are concerning. Direct detection of SARS-CoV-2 from a patient with MIS-C might suggest its contribution to its clinical manifestation. As the COVID-19 pandemic expands over time, however, the presence of the specific SARS-CoV-2 antibody alone may not be sufficient to explain the causal relationship in which

Croup is an acute upper respiratory disease primarily caused by the parainfluenza virus. Owing to inflammation and edema of the upper airways, children present with barky cough and stridor, and some may experience respiratory distress. We investigated children aged < 5 years with coronavirus disease 2019 (COVID-19) admitted to two hospitals in Seoul, South Korea, and observed a spike in croup cases during the omicron surge. Among the 569 children admitted from March 1, 2021 to February 25, 2022, 21 children (3.7%) had croup, and the proportion of croup cases was significantly higher during the omicron wave than that during the delta wave (12.4% vs. 1.2%, P < 0.001). With the immediate administration of corticosteroids and epinephrine via nebulizer, the symptoms improved rapidly. During the current omicron surge, careful monitoring of the symptoms of croup in young children is needed for the diagnosis of COVID-19 and its timely management.

BackgroundMycobacterium bovis Bacille Calmette-Guérin (BCG) osteitis, a rare complication of BCG vaccination, has not been well investigated in Korea. This study aimed to evaluate the clinical characteristics of BCG osteitis during the recent 10 years in Korea.MethodsChildren diagnosed with BCG osteitis at the Seoul National University Children's Hospital from January 2007 to March 2018 were included. M. bovis BCG was confirmed by multiplex polymerase chain reaction (PCR) in the affected bone. BCG immunization status and clinical information were reviewed retrospectively.ResultsTwenty-one patients were diagnosed with BCG osteitis and their median symptom onset from BCG vaccination was 13.8 months (range, 6.0–32.5). Sixteen children (76.2%) received Tokyo-172 vaccine by percutaneous multiple puncture method, while four (19.0%) and one (4.8%) received intradermal Tokyo-172 and Danish strain, respectively. Common presenting symptoms were swelling (76.2%), limited movement of the affected site (63.2%), and pain (61.9%) while fever was only accompanied in 19.0%. Femur (33.3%) and the tarsal bones (23.8%) were the most frequently involved sites; and demarcated osteolytic lesions (63.1%) and cortical breakages (42.1%) were observed on plain radiographs. Surgical drainage was performed in 90.5%, and 33.3% of them required repeated surgical interventions due to persistent symptoms. Antituberculosis medications were administered for a median duration of 12 months (range, 12–31). Most patients recovered without evident sequelae.ConclusionHighly suspecting BCG osteitis based on clinical manifestations is important for prompt management. A comprehensive national surveillance system is needed to understand the exact incidence of serious adverse reactions following BCG vaccination and establish safe vaccination policy in Korea.

In areas with high prevalence of macrolide-resistant Mycoplasma pneumoniae (MRMP) pneumonia, treatment in children has become challenging. This study aimed to analyze the efficacy of macrolides and doxycycline with regard to the presence of macrolide resistance. We analyzed children with MP pneumonia during the two recent epidemics of 2014–2015 and 2019–2020 from four hospitals in Korea. Nasopharyngeal samples were obtained from children with pneumonia for MP cultures and polymerase chain reaction (PCR). Macrolide resistance was determined by the analysis of 23S rRNA gene transition. Time to defervescence and to chest X-ray improvement were analyzed. Of 145 cases, the median age was 5.0 years and MRMP accounted for 59 (40.7%). Among macrolide-susceptible MP (MSMP), 78 (90.7%) were treated with macrolides and 21 (35.6%) in the MRMP group with doxycycline. In MRMP pneumonia, shorter days to defervescence (2 vs. 5 days, p < 0.001) and to chest X-ray improvement (3 vs. 6 days, p < 0.001) in the doxycycline group than in the macrolide group was observed, whereas no differences were observed among children with MSMP pneumonia. Compared to macrolides, treatment with doxycycline resulted in better outcomes with a shorter time to defervescence and to chest X-ray improvement among children with MRMP pneumonia.