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BACKGROUND: There has been much discussion about coronavirus disease 2019 (COVID-19) and the virus that causes it, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in children and adolescents, since the pandemic was recognised in early 2020. Understanding their role in this pandemic is important for the development of appropriate prevention measures. OBJECTIVE: To summarise evidence about three aspects of SARS-CoV-2 and COVID-19 in children and adolescents: (1) severity of SARS-CoV-2 presentation, (2) risk of SARS-CoV-2 infection and (3) risk of transmitting SARS-CoV-2. METHODS: We searched PubMed and MedRxiv for studies on SARS-CoV-2 and COVID-19 in children and adolescents from January 2020 to 21 January 2021. The electronic search was supplemented by papers found in a manual search or suggested by experts up to 29 March 2021. We included case reports, cross-sectional studies, cohort studies, narrative reviews or viewpoints, systematic reviews and modelling studies. We synthesised the information descriptively and attempted to report findings separately for: infants and small children (0–5 years) who are mostly pre-school; school children (6–12 years) broadly covering primary school years; and adolescents (13–17 years). RESULTS: Of 2778 screened articles, we included 63 (20 case reports, 18 cross-sectional studies, 8 cohort studies, 6 narrative reviews or viewpoints, 10 systematic reviews and 1 modelling study). Children (≤12 years of age) and adolescents (13–17 years of age) usually present with mild disease, with few requiring intensive care treatment. A minority of children of all ages (<18 years) remains asymptomatic throughout the course of infection. In serological studies, reported symptoms are similar in children with and without SARS-CoV-2 antibodies. Children and adolescents can acquire and transmit SARS-CoV-2. The risks of acquiring and transmitting SARS-CoV-2 seems to increase with age. There was limited information about SARS-CoV-2 variants of concern. Poor reporting of age groups and contextual factors such as levels of community transmission, school closures and other non-pharmaceutical interventions make synthesis of findings across studies difficult. CONCLUSIONS: The clinical presentation and role of children and adolescents in SARS-CoV-2 susceptibility and transmission needs further investigation, particularly with regard to variants of concern. Large, prospective studies that attempt to minimise biases in design, are analysed appropriately and reported comprehensively should be conducted.

2+ sensitivity of vascular smooth muscle (VSM) allows for vasodilation without lowering of cytosolic Ca2+ . This may be particularly important in states requiring maintained dilation, such as hypoxia. AMP-related kinase (AMPK) is an important cellular energy sensor in VSM. Regulation of Ca 2+ sensitivity usually is attributed to myosin light chain phosphatase activity, but findings in non-VSM identified changes in the actin cytoskeleton. The potential role of AMPK in this setting is widely unknown.Objective: To assess the influence of AMPK on the actin cytoskeleton in VSM of resistance arteries with regard to potential Ca 2+ desensitization of VSM contractile apparatus. Methods and Results: AMPK induced a slowly developing dilation at unchanged cytosolic Ca2+ levels in potassium chloride-constricted intact arteries isolated from mouse mesenteric tissue. This dilation was not associated with changes in phosphorylation of myosin light chain or of myosin light chain phosphatase regulatory subunit. Using ultracentrifugation and confocal microscopy, we found that AMPK induced depolymerization of F-actin (filamentous actin). Imaging of arteries from LifeAct mice showed F-actin rarefaction in the midcellular portion of VSM. Immunoblotting revealed that this was associated with activation of the actin severing factor cofilin. Coimmunoprecipitation experiments indicated that AMPK leads to the liberation of cofilin from 14-3-3 protein.