The overlap of coronavirus disease 2019 (COVID-19) with other common respiratory pathogens may complicate the course of the disease and prognosis. The aim of the study was to evaluate the rates, characteristics, and outcomes of pediatric patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory syncytial virus (RSV), influenza A/B infections, and their coinfections. A single-center prospective cross-sectional study was performed at the pediatric emergency department in Vilnius from 1 October 2021 to 30 April 2022. In total, 5127 children were screened for SARS-CoV-2, RSV, and influenza A/B. SARS-CoV-2 PCR tests were positive for 21.0% of children (1074/5127). The coinfection rate of respiratory viruses (RSV, influenza A) in patients with COVID-19 was 7.2% (77/1074). Among the 4053 SARS-CoV-2 negative patients, RSV was diagnosed in 405 (10.0%) patients and influenza A/B in 827 (20.4%) patients. Patients with COVID-19 and coinfection did not have a more severe clinical course than those with RSV or influenza infection alone. RSV and SARS-CoV-2 primarily affected younger patients (up to 2 years), while the influenza was more common in older children (4–10 years). Patients infected with RSV were more severely ill, reflected by higher hospitalization proportion and need for respiratory support.

Background: Since the start of the COVID-19 pandemic, the epidemiology of acute respiratory infections (ARIs) has continually changed, making it difficult to predict. Our study aimed to evaluate epidemiological changes and clinical outcomes of ARIs in pediatric patients in the post-lockdown period. Methods: A single-center retrospective cross-sectional study was performed in one of the largest pediatric emergency departments in Lithuania during two cold seasons–from October 1, 2021, to April 30, 2022 (Season I) and in the same period in 2022–2023 (Season II). Patients under 18 years of age who had been tested for COVID-19 were enrolled in the study. Additional data about other respiratory pathogens in the study group (specifically influenza A/B, respiratory syncytial virus (RSV) and group A Streptococcus (GAS)), were included. Results: During both seasons of our study, 19,366 children were screened for COVID-19. Positive tests for COVID-19 decreased from 14.5% in Season I to 5.9% in Season II, while at the same time, the rates of other infections increased significantly: influenza from 17.5% to 27.1%, RSV from 8.8% to 27.6%, and GAS from 8.4% to 44%, respectively. In Season II, COVID-19 infection presented in fewer admissions to pediatric intensive care (0.8% vs. 3.7%, p<0.01) and there were no deaths, while influenza presented in a higher proportion of hospitalizations (10.5% vs. 6.1%, p<0.01) and there was one death. The proportion of RSV hospitalizations also increased in Season II (34.6% vs. 44.0%, p<0.01). Conclusions: The early post-lockdown period saw a decline of COVID-19 and re-emergence of influenza, RSV and GAS infections in children. In Season II, COVID-19 cases became milder contrary to influenza. RSV infection contributed significantly to hospitalizations for respiratory infections in children in both seasons, particularly in Season II. Coinfections were not associated with a more severe course of the disease.

The wide spectrum of COVID-19 symptoms complicates the selection of target groups for screening. We aimed to compare data of children screened for COVID-19 at the pediatric emergency department in Vilnius between different phases throughout 1 year (Phase I: March–May, 2020; Phase II: June–September, 2020; and Phase III: October, 2020–February, 2021) and to evaluate the possible predictors of the disease. SARS-CoV-2 PCR tests were positive for 2.7% of tested children (248/9,238), significantly higher during the Phase III (5.5%) compared with the Phase I (0.6%,p= 0.000) and Phase II (0.3%,p= 0.000). Infants and teenagers (12–17 years) accounted for a larger proportion of COVID-19 patients (24.6 and 26.2%, respectively) compared to other age groups: 1–2 years (18.9%), 3–6 years (14.9%), and 7–11 years (15.3%). There were more COVID-19 cases among children with a known SARS-CoV-2 exposure compared to those who did not declare any contact (18.2 vs. 1.1%,p= 0000). When symptoms were adjusted for age, gender and known exposure to SARS-CoV-2, we found that fever (OR 2.66; 95% CI 1.89–3.81), pharyngitis (OR 1.35; 95% CI 1.01–1.80), headache (OR 1.81; 95% CI 1.09–2.90), and anosmia/ageusia (OR 6.47; 95% CI 1.61–22.47) were the most significant predictors.Conclusion:Although high numbers of testing were maintained throughout the year, the positive test results were significantly higher during the Phase III. Age (<1 year, 12–17 years), a history of exposure to SARS-CoV-2 and some symptoms, such as fever, pharyngitis, headache and anosmia/ageusia could aid in targeting groups for screening for COVID-19 in children.

Background and Objectives: Due to its link with the SARS-CoV-2, Multisystem Inflammatory Syndrome in Children (MIS-C) gained global attention as a serious condition that requires hospital care. Our study aimed to present the clinical and laboratory characteristics of MIS-C patients by age group and intensive care unit (ICU) admission status and assess early echocardiographic changes. Materials and Methods: A single-center partly retrospective, partly prospective observational cohort study was performed from December 2020 to June 2024. The study included 42 patients aged between 1 month and 18 years who were diagnosed with MIS-C and gave informed consent. Results: The median age was 6.5 years (IQR 2.0–9.3). The predominant symptoms were cardiovascular (88.1%), mucocutaneous (85.7%) and gastrointestinal (76.2%). Five children (11.9%) developed shock. About two-thirds of patients (66.7%) were admitted to the ICU. Adolescents (≥12 years) were less likely to exhibit mucocutaneous or cardiovascular symptoms and thus less frequently having Kawasaki—like disease symptoms compared with other age groups (<5 years or 5–11 years). Lymphopenia was more common among patients aged 5 years and older. Adolescents had higher procalcitonin (PCT) and a lower estimated glomerular filtration rate. Troponin I and B-type natriuretic peptide (BNP) levels were higher in children aged 5–11 years, while ferritin levels were lower among the youngest (<5 years). Patients treated at the ICU were more likely to have cardiovascular and respiratory symptoms, as well as a history of symptomatic COVID-19, higher C-reactive protein (CRP), PCT, BNP and lower albumin levels. Echocardiographic abnormalities were found in 71.4% of cases. During hospitalization, left ventricular ejection fraction values increased significantly (p < 0.001) over 12 (IQR 9.0–14.0) days. Conclusions: Symptoms and laboratory markers of MIS-C vary according to age. Higher CRP, PCT, BNP and hypoalbuminemia are predictors of MIS-C severity. Cardiovascular involvement is common and might be severe, but rapid resolution is encouraging.