Objectives: The aim of this study is to identify the epidemiological, clinical, and laboratory features of coronavirus disease 2019 (COVID-19) in children.Methods: A retrospective study was conducted by pediatric infectious disease specialists from 32 different hospitals from all over Turkey by case record forms. Pediatric cases who were diagnosed as COVID-19 between March 16, 2020, and June 15, 2020 were included. Case characteristics including age, sex, dates of disease onset and diagnosis, family, and contact information were recorded. Clinical data, including the duration and severity of symptoms, were also collected. Laboratory parameters like biochemical tests and complete blood count, chest X-ray, and chest computed tomography (CT) were determined.Results: There were 1,156 confirmed pediatric COVID-19 cases. In total, male cases constituted 50.3% (n = 582) and females constituted 49.7% (n = 574). The median age of the confirmed cases was 10.75 years (4.5–14.6). Of the total cases, 90 were younger than 1 year of age (7.8%), 108 were 1–3 years of age (9.3%), 148 were 3–6 years of age (12.8%), 298 were 6–12 years of age (25.8%), 233 were 12–15 years of age (20.2%), and 268 cases were older than 15 years of age (23.2%). The most common symptom of the patients at the first visit was fever (50.4%) (n = 583) for a median of 2 days (IQR: 1–3 days). Fever was median at 38.4°C (38.0–38.7°C). The second most common symptom was cough (n = 543, 46.9%). The other common symptoms were sore throat (n = 143, 12.4%), myalgia (n = 141, 12.2%), dyspnea (n = 118, 10.2%), diarrhea (n = 112, 9.7%), stomachache (n = 71, 6.1%), and nasal discharge (n = 63, 5.4%). When patients were classified according to disease severity, 263 (22.7%) patients were asymptomatic, 668 (57.7%) patients had mild disease, 209 (18.1%) had moderate disease, and 16 (1.5%) cases had severe disease. One hundred and forty-nine (12.9%) cases had underlying diseases among the total cases; 56% of the patients who had severe disease had an underlying condition (p < 0.01). The need for hospitalization did not differ between patients who had an underlying condition and those who do not have (p = 0.38), but the need for intensive care was higher in patients who had an underlying condition (p < 0.01). Forty-seven (31.5%) of the cases having underlying conditions had asthma or lung disease (38 of them had asthma).Conclusions: To the best of our knowledge, this is one of the largest pediatric data about confirmed COVID-19 cases. Children from all ages appear to be susceptible to COVID-19, and there is a significant difference in symptomatology and laboratory findings by means of age distribution.

Aims: Limited data about disease management strategies are available for pediatric patients with coronavirus disease-2019, particularly in Turkey. This study aimed to share the data on patients aged under 18 years in our country to be beneficial for understanding the disease course in children. Methods: A retrospective review of the medical records of pediatric patients aged under 18 years who were confirmed as coronavirus disease-2019 between March 11, and June 23, 2020, and were admitted to our hospitals was conducted. Results: A total of 220 pediatric patients with coronavirus disease-2019 were evaluated, of which 48.2% were boys, with a median age of 10 years, and 9.5% had underlying diseases. Patients were classified according to severity, with the percentages of asymptomatic, mild, moderate, and critical/severe cases determined to be 25.5%, 45%, 26.8%, and 2.7%, respectively. Extracorporeal membrane oxygenation was required in two patients (0.9%) and mechanical ventilation in three (1.4%). Targeted therapies were used in six patients (2.7%), with hydroxychloroquine being the most commonly used agent either alone (one patient) or in combination with favipiravir (five patients). Two patients (0.9%) died, and nine (4.1%) were still hospitalized during the study period. Conclusion: Although the disease course of coronavirus disease-2019 seems to be mild in children, critical illness is significant, and the treatment strategy primarily should consist of supportive care according to our preliminary observations.

Objective We aimed to describe the typical clinical and laboratory features and treatment of children diagnosed with multisystem inflammatory syndrome in children (MIS-C) and to understand the differences as compared to severe/critical pediatric cases with COVID-19 in an eastern Mediterranean country. Methods Children (aged <18 years) who diagnosed with MIS-C and severe/critical pediatric cases with COVID-19 and were admitted to hospital between March 26 and November 3, 2020 were enrolled in the study. Results A total of 52 patients, 22 patients diagnosed with COVID-19 with severe/critical disease course and 30 patients diagnosed with MIS-C, were included in the study. Although severe COVID-19 cases and cases with MIS-C share many clinical and laboratory features, MIS-C cases had longer fever duration and higher rate of the existence of rash, conjunctival injection, peripheral edema, abdominal pain, altered mental status, and myalgia than in severe cases (p<0.001 for each). Of all, 53.3% of MIS-C cases had the evidence of myocardial involvement as compared to severe cases (27.2%). Additionally, C-reactive protein (CRP) and white blood cell (WBC) are the independent predictors for the diagnosis of MIS-C, particularly in the existence of conjunctival injection and rash. Corticosteroids, intravenous immunoglobulin (IVIG), and biologic immunomodulatory treatments were mainly used in MIS-C cases rather than cases with severe disease course. There were only three deaths among 52 patients, one of whom had Burkitt lymphoma and the two cases with severe COVID-19 of late referral. Conclusion Differences between clinical presentations, acute phase responses, organ involvements, and management strategies indicate that MIS-C might be a distinct immunopathogenic disease as compared to pediatric COVID-19. Conjunctival injection and higher CRP and low WBC count are reliable diagnostic parameters for MIS-C cases. Keywords Kawasaki disease. Pediatrics. Hyperinflammation. Multisystem inflammatory syndrome in children (MIS-C). Multisystem inflammatory syndrome in adults (MIS-A) Key Points • MIS-C cases had longer fever duration and higher rate of the existence of rash, conjunctival injection, peripheral edema, abdominal pain, altered mental status, and myalgia than in severe/critical pediatric cases with COVID-19. • Higher CRP and low total WBC count are the independent predictors for the diagnosis of MIS-C. • MIS-C might be a distinct immunopathogenic disease as compared to pediatric COVID-19.

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Introduction: Antibody response developed within 2-3 weeks after exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown to decrease over time; however, there is limited data about antibody levels at 6 months or later postinfection, particularly in children. Materials and Method:A prospective multicenter study was performed using 315 samples of 74 confirmed and 10 probable coronavirus disease 2019 pediatric cases. About 20% of these cases were classified as asymptomatic, 74% as mild/moderate and 6% as severe/critical. Patients were included if at least 2 samples were available. The antibody response was classified as either early-period or late-period (14 days-3 months and after 6 months, respectively) for IgG response whereas IgA response was tested on various time intervals, including as early as 4 days up to 3 months. Euroimmun Anti-SARS-CoV-2 IgG and IgA and Genscript SARS-CoV-2 Surrogate Virus Neutralization Kits were used for antibody detection. Results: There was no difference between the early-period and late-period IgG positivity (P = 0.1). However, the median IgG levels were 11.98 in the early periods and 4.05 in the late periods, with a significance of P < 0.001. Although the decrease in IgG levels was significant in asymptomatic and mild/moderate cases (P < 0.008 and P < 0.001, respectively), the decrease in severe/critical cases was moderate (P = 0.285). The sensitivity of the IgG after 15 days was higher than 94%, and the sensitivity of IgA was 88% on days 8-15. Conclusion: SARS-CoV-2 IgG antibody levels decreased after 6 months. The decrease was moderate in severe/critical cases. Overall, 95.8% of the patients remained positive up to 9 months after infection. Although the IgA response may be useful early on, the IgG response is useful after 14 days.

Crimean-Congo hemorrhagic fever (CCHF), endemic in certain regions of the world, is listed as a priority disease with pandemic potential. Since CCHF was first identified in Turkey, children have been known to experience milder disease than adults. However, during the COVID-19 pandemic, we observed an unusually severe disease course, including hemophagocytic lymphohistiocytosis (HLH). We examined cytokine/chemokine profiles of 9/12 case-patients compared with healthy controls at 3 time intervals. Interferon pathway–related cytokines/chemokines, including interleukin (IL) 18, macrophage inflammatory protein 3α, and IL-33, were elevated, but tumor necrosis factor-α, IL-6, CXCL8 (formerly IL-8), and cytokines acting through C-C chemokine receptor 2 and CCR5 were lower among case-patients than controls. Interferon pathway activation and cytokines/chemokines acting through CCR2 and CCR5 improved health results among children with severe CCHF. Children can experience severe CCHF, including HLH, and HLH secondary to CCHF can be successfully treated with intravenous immunoglobulin and steroid therapy.

The authors regrets that In the original published version of this article one co-author "İlker Ertugrul" was inadvertently omitted in the authorship section. The author name has been added above. The original article has been corrected. Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Objective The frequency of coinfections in pediatric Coronavirus disease 2019 (COVID-19) cases and their impact on the clinical course are not fully understood. We aimed to investigate the viral and bacterial respiratory pathogens in children admitted to the pediatric emergency department (PED), their clinical course, and the presence of coinfections during the early months of the COVID-19 pandemic. Methods Clinical, laboratory and radiological findings, viral and bacterial pathogens detected by multiplex polymerase chain reaction (PCR) tests in nasopharyngeal swabs, clinical course, and treatments of all children who were tested for severe acute respiratory coronavirus 2 (SARS-CoV-2) at the PED between March 16 and May 15, 2020, were recorded. SARS-CoV-2 PCR-positive and negative groups were compared. Results Out of 570 patients tested for SARS-CoV-2 during the study period, 43 were found positive (7.5%). Non-SARS-CoV-2 viral pathogens were more common in the SARS-CoV-2 PCR-negative group than the SARS-CoV-2 PCR-positive group (13.2%, n = 68 versus 4.7%, n = 2), but this result was not statistically significant. Leukocyte, neutrophil, lymphocyte, and platelet counts were lower in SARS-CoV-2 PCR-positive group. Bacterial panel positivity was significantly higher in the SARS-CoV-2 PCR-positive group compared with the SARS-CoV-2 PCR-negative group (52%, n = 12 versus 28%, n = 91; p < 0.05). The presence of coinfection did not alter the course of therapy in SARS-CoV-2 PCR-positive cases. Conclusion While viral coinfections were rare, bacterial panel positivity was common in children with COVID-19, but this had not influenced management decisions. The limitations of the tests should be kept in mind while interpreting the results.