Acute and Postacute Clinical Characteristics of Coronavirus Disease 2019 in Children in Japan.

BACKGROUND: The clinical features of coronavirus disease 2019 (COVID-19) in children have been changing because of the emergence and rapid spread of variants of concern (VOC). The increase in cases infected with VOC has brought concern with persistent symptoms after COVID-19 in children. This survey aimed to analyze the clinical manifestations and persistent symptoms of pediatric COVID-19 cases in Japan. METHODS: We analyzed the clinical manifestations of pediatric COVID-19 cases reported between February 2020 and April 2022 in Japan, using a dedicated database updated voluntarily by the members of the Japan Pediatric Society. Using the same database, we also analyzed persistent symptoms after COVID-19 in children who were diagnosed between February 2020 and November 2021. RESULTS: A total of 5411 and 1697 pediatric COVID-19 cases were included for analyzing clinical manifestations and persistent symptoms, respectively. During the Omicron variant predominant period, the percentage of patients with seizures increased to 13.4% and 7.4% in patient groups 1-4 and 5-11 years of age, respectively, compared with the pre-Delta (1.3%, 0.4%) or Delta period (3.1%, 0.0%). Persistent and present symptoms after 28 days of COVID-19 onset were reported in 55 (3.2%). CONCLUSIONS: Our survey showed that the rate of symptomatic pediatric COVID-19 cases increased gradually, especially during the Omicron variant predominant period, and a certain percentage of pediatric cases had persistent symptoms. Certain percentages of pediatric COVID-19 patients had severe complications or prolonged symptoms. Further studies are needed to follow such patients.

Hydrophobic Alpha-Helical Short Peptides in Overlapping Reading Frames of the Coronavirus Genome.

In this study, we show that the coronavirus (CoV) genome may encode many functional hydrophobic alpha-helical peptides (HAHPs) in overlapping reading frames of major coronaviral proteins throughout the entire viral genome. These HAHPs can theoretically be expressed from non-canonical sub-genomic (sg)RNAs that are synthesized in substantial amounts in infected cells. We selected and analyzed five and six HAHPs encoded in the S gene regions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle East respiratory syndrome coronavirus (MERS-CoV), respectively. Two and three HAHPs derived from SARS-CoV-2 and MERS-CoV, respectively, specifically interacted with both the SARS-CoV-2 and MERS-CoV S proteins and inhibited their membrane fusion activity. Furthermore, one of the SARS-CoV-2 HAHPs specifically inhibited viral RNA synthesis by accumulating at the site of viral RNA synthesis. Our data show that a group of HAHPs in the coronaviral genome potentially has a regulatory role in viral propagation.

Changes in virus detection in hospitalized children before and after the severe acute respiratory syndrome coronavirus 2 pandemic.

The impact of strengthening preventive measures against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on the prevalence of respiratory viruses in children was examined. After the SARS-CoV-2 pandemic, the rate of multiple virus detection among hospitalized children decreased. Immediately after the SARS-CoV-2 pandemic, respiratory syncytial and parainfluenza viruses were rarely detected and subsequently reemerged. Human metapneumovirus and influenza virus were not consistently detected. Non-enveloped viruses (bocavirus, rhinovirus, and adenovirus) were detected to some extent even after the pandemic. Epidemic-suppressed infectious diseases may reemerge as susceptibility accumulates in the population and should continue to be monitored.

Epidemiological and clinical characteristics of infections with seasonal human coronavirus and respiratory syncytial virus in hospitalized children immediately before the coronavirus disease 2019 pandemic.

INTRODUCTION: Seasonal human coronavirus (HCoV)-229E, -NL63, -OC43, and -HKU1 are seasonal coronaviruses that cause colds in humans. However, the clinical characteristics of pediatric inpatients infected with HCoVs are unclear. This study aimed to compare and clarify the epidemiological and clinical features of HCoVs and respiratory syncytial virus (RSV), which commonly causes severe respiratory infections in children. METHODS: Nasopharyngeal swabs were collected from all pediatric inpatients with respiratory symptoms at two secondary medical institutions in Fukushima, Japan. Eighteen respiratory viruses, including RSV and four HCoVs, were detected via reverse transcription-polymerase chain reaction. RESULTS: Of the 1757 specimens tested, viruses were detected in 1272 specimens (72.4%), with 789 single (44.9%) and 483 multiple virus detections (27.5%). RSV was detected in 639 patients (36.4%) with no difference in clinical characteristics between RSV-A and RSV-B. HCoV was detected in 84 patients (4.7%): OC43, NL63, HKU1, and 229E in 25 (1.4%), 26 (1.5%), 23 (1.3%), and 16 patients (0.9%), respectively. Patients with HCoV monoinfection (n = 35) had a significantly shorter period from onset to hospitalization (median [interquartile range] days, 2 [1-4.5] vs. 4 [2-5]), significantly shorter hospitalization stays (4 [3-5] vs. 5 [4-6]), and more cases of upper respiratory infections (37.1% vs. 3.9%) and croup (17.1% vs. 0.3%) but less cases of lower respiratory infection (54.3% vs. 94.8%) than patients with RSV monoinfection (n = 362). CONCLUSION: Seasonal HCoV-infected patients account for approximately 5% of children hospitalized for respiratory tract infections and have fewer lower respiratory infections and shorter hospital stays than RSV-infected patients.

The clinical characteristics of pediatric coronavirus disease 2019 in 2020 in Japan.

BACKGROUND: The COVID-19 pandemic has affected the lives of people of all ages. Most reports on pediatric cases suggest that children experience fewer and milder symptoms than do adults. This is the first nationwide study in Japan focusing on pediatric cases reported by pediatricians, including cases with no or mild symptoms. METHODS: We analyzed the epidemiological and clinical characteristics and transmission patterns of 840 pediatric (<16 years old) COVID-19 cases reported between February and December 2020 in Japan, using a dedicated database which was maintained voluntarily by members of the Japan Pediatric Society. RESULTS: Almost half of the patients (47.7%) were asymptomatic, while most of the others presented mild symptoms. At the time of admission or first outpatient clinic visit, 84.0% of the cases were afebrile (<37.5°C). In total, 609 cases (72.5%) were exposed to COVID-19-positive household members. We analyzed the influence of nationwide school closures that were introduced in March 2020 on COVID-19 transmission routes among children in Japan. Transmission within households occurred most frequently, with no significant difference between the periods before and after declaring nationwide school closures (70.9% and 74.5%, respectively). CONCLUSIONS: COVID-19 symptoms in children are less severe than those in adults. School closure appeared to have a limited effect on transmission. Controlling household transmission from adult family members is the most important measure for prevention of COVID-19 among children.