@ERSpublications Epidemiological evidence shows that SARS-CoV-2 infection in children is less frequent and severe than adults. Age-related ACE2 receptor expression, lymphocyte count and trained immunity might be the keystone to reveal children's secret. https://bit.ly/2QWpWxK Cite this article as: Cristiani L, Mancino E, Matera L, et al. Will children reveal their secret? The coronavirus dilemma. Eur Respir J 2020; 55: 2000749 [https://doi.

The diffusion of the SARS‐CoV‐2 virus and the implementation of restrictive measures led to a drastic reduction of respiratory syncytial virus (RSV) diffusion. Few RSV cases have been detected worldwide, even after the removal of the restrictions. We review the current literature and present possible explanations on why there has been a significant reduction of RSV detection during the COVID‐19 pandemic. We also hypothesize what may happen when RSV begins to circulate again. The increase of an immunologically naïve population, with infants born from mothers who have not reinforced their immunity to RSV, could lead to greater RSV epidemics in the coming seasons. It is crucial to prepare the scientific community and to keep RSV surveillance active to avoid dramatic consequences.

Novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) became pandemic by the end of March 2020. In contrast to the 2002–2003 SARS-CoV outbreak, which had a higher pathogenicity and lead to higher mortality rates, SARSCoV-2 infection appears to be much more contagious. Moreover, many SARS-CoV-2 infected patients are reported to develop low-titer neutralizing antibody and usually suffer prolonged illness, suggesting a more effective SARS-CoV-2 immune surveillance evasion than SARS-CoV. This paper summarizes the current state of art about the differences and similarities between the pathogenesis of the two coronaviruses, focusing on receptor binding domain, host cell entry and protease activation. Such differences may provide insight into possible intervention strategies to fight the pandemic.

Background Two sequelae of pediatric COVID-19 have been identified, the multisystem inflammatory syndrome in children (MIS-C) and the long COVID. Long COVID is much less precisely defined and includes all the persistent or new clinical manifestations evidenced in subjects previously infected by SARS-CoV-2 beyond the period of the acute infection and that cannot be explained by an alternative diagnosis. In this Intersociety Consensus, present knowledge on pediatric long COVID as well as how to identify and manage children with long COVID are discussed. Main findings Although the true prevalence of long COVID in pediatrics is not exactly determined, it seems appropriate to recommend evaluating the presence of symptoms suggestive of long COVID near the end of the acute phase of the disease, between 4 and 12 weeks from this. Long COVID in children and adolescents should be suspected in presence of persistent headache and fatigue, sleep disturbance, difficulty in concentrating, abdominal pain, myalgia or arthralgia. Persistent chest pain, stomach pain, diarrhea, heart palpitations, and skin lesions should be considered as possible symptoms of long COVID. It is recommended that the primary care pediatrician visits all subjects with a suspected or a proven diagnosis of SARS-CoV-2 infection after 4 weeks to check for the presence of symptoms of previously unknown disease. In any case, a further check-up by the primary care pediatrician should be scheduled 3 months after the diagnosis of SARS-CoV-2 infection to confirm normality or to address emerging problems. The subjects who present symptoms of any organic problem must undergo a thorough evaluation of the same, with a possible request for clinical, laboratory and / or radiological in-depth analysis in case of need. Children and adolescents with clear symptoms of mental stress will need to be followed up by existing local services for problems of this type. Conclusions Pediatric long COVID is a relevant problem that involve a considerable proportion of children and adolescents. Prognosis of these cases is generally good as in most of them symptoms disappear spontaneously. The few children with significant medical problems should be early identified after the acute phase of the infection and adequately managed to assure complete resolution. A relevant psychological support for all the children during COVID-19 pandemic must be organized by health authorities and government that have to treat this as a public health issue.

Background Bronchiolitis is the most common acute viral infection of the lower respiratory tract in infants. Clinical severity is associated with different risk factors; however, no clinical, laboratory, or radiological findings are able to predict the course of the disease in full‐term infants. Lung ultrasound (LUS) is a valid technique for the diagnosis and evaluation of pediatric respiratory diseases. Aims The aim of our study was to correlate an LUS score with a clinical score, to describe lung ultrasound findings in cases and controls, and to compare LUS findings with chest X‐ray (CXR) in infants hospitalized with bronchiolitis. Methods We conducted a single‐center, longitudinal, prospective study on 92 infants. Sixty‐three out of 92 infants were hospitalized for acute bronchiolitis (cases) and twenty‐nine out of 92 for diseases not involving the respiratory system (controls). All patients with bronchiolitis underwent a clinical evaluation with the assignment of a clinical severity score and performed lung ultrasound with the assignment of an LUS score. Twenty‐three out of 63 infants with bronchiolitis underwent also a CXR for clinical indications. Control infants performed only LUS. Results In infants with bronchiolitis LUS score showed a positive correlation with the clinical score (r = .62, p < .001) and the length of hospitalization (r = .42; p < .001). The need of oxygen therapy was more frequent in the patients with higher LUS score (p < .001). LUS findings observed in the cases were the presence of B‐lines, subpleural consolidations, and abnormalities of the pleural line. No LUS alterations were observed in the controls. In patients who performed LUS and CXR, we found a correlation between the presence of abnormalities of the pleural line with LUS and the presence of air trapping with CXR (r = .55; p = .007).

Severe Acute Respiratory Syndrome – Coronavirus – 2 (SARS-CoV-2) and its related Coronavirus Disease – 19 (COVID-19) has become a health emergency worldwide. The medical community has been concerned since the beginning of the outbreak about the potential impact of COVID-19 in children, especially in those with underlying chronic diseases. Fortunately, COVID-19 has been reported to be less severe in children than in adults. However, epidemiologic and clinical data are scarce. Children show unique features of SARS-CoV-2 involvement that may account for the low rate of infection and death in this age group. The purpose of this review is to summarize the most relevant evidence of COVID-19 in children highlighting similarities and differences with adults.

Aim Emergency room admissions have decreased globally during the COVID‐19 pandemic, particularly for respiratory diseases. We evaluated hospital admissions for respiratory diseases in the first year of the Italian pandemic and compared them with the corresponding period in 2016–2017. Methods The study was carried out at the Sapienza University in Rome, Italy, and covered 9 March to 28 February 2020–2021 and 2016–2017. We tested 85 hospitalised children who were negative for the virus that causes COVID‐19 in 2020–2021 and compared them with 476 hospitalised children from 2016–2017, as we had also tested nasal washing samples for 14 respiratory viruses during that period. Results Hospitalisations for acute respiratory tract infections were 82.2% lower in 2020–2021 than 2016–2017. The respiratory syncytial virus (RSV) and several other viruses were detected less frequently during the pandemic. An extraordinary finding was that rhinoviruses remained seasonal. In 2020–2021, we detected a virus in 54.1% of the hospitalised children: rhinoviruses in 41, RSV in 4 and other viruses in 1. This was significantly lower than the 71.6% in 2016–2017: RSV in 130, rhinoviruses in 128 and other viruses in 83. Conclusion Pandemic measures dramatically reduced childhood respiratory infections, particularly RSV, but were less effective at reducing rhinoviruses.

Background: The heterogeneity of bronchiolitis may imply or reflect a different predisposition to respiratory sequelae.Objective: Our aim was to investigate whether, among infants hospitalized with bronchiolitis, different clinical profiles extracted by latent class analysis (LCA) are associated with different risks of wheezing.Methods: Over 15 consecutive epidemic seasons (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019), we prospectively enrolled infants <1 year hospitalized for the first episode of bronchiolitis in a single tertiary hospital. A detailed clinical questionnaire was filled for each infant. LCA was applied to differentiate bronchiolitis phenotypes, and after hospital discharge, a phone interview was performed annually to record the presence of wheezing episodes. Adjusted multivariate regression analyses were run to investigate the risk of wheezing during 7 years follow-up according to clinical phenotypes.Results: LCA performed on 1312 infants resulted in a three-class model. Profile 1 (65.5%): moderate bronchiolitis; Profile 2 (6.1%): severe bronchiolitis; and Profile 3(28.4%): bronchiolitis infants with high eosinophils blood count. At 1 year of follow up, about 50% of children presented wheezing in each profile. Compared to Profile 1, the adjusted odds ratio (OR) of having wheezing episodes was significantly higher in Profile 2 at 2, 3, and 4 years of follow-up. At 7 years, Profile 3 had an adjusted OR = 2.58, higher than Profile 2 (adjusted OR = 2.29).Conclusions: LCA clearly identified a "moderate", "severe," and "high eosinophils blood count" bronchiolitis. During the first 4 years after bronchiolitis, the "severe" profile showed the higher risk of wheezing, but after 7 years this risk seems higher in the "high eosinophils blood count" group.