COVID-19 evolution in pediatric emergency department patients in Madrid, Spain: a single-center, retrospective study.

Introduction: COVID-19, caused by the SARS-CoV-2 virus, had a significant global impact since its emergence in December 2019. In Spain, the pandemic caused multiple waves of infections, with variations in clinical presentation and predominant viral strains. This study analyzed the evolution of COVID-19 in pediatric patients in a pediatric emergency department in Madrid (Spain), focusing on the changes in clinical manifestations over time.

Methods: This single-center, retrospective study was conducted from March 2020 to October 2024, including pediatric patients aged 0-18 years with confirmed SARS-CoV-2 infection. Data collected included demographic characteristics, clinical manifestations, and hospital admission rates. The sample was divided into groups based on the predominant circulating variant during specific periods.

Results: A total of 1,949 confirmed COVID-19 cases were analyzed. The median age of the patients was 1.2 years (IQR: 0.4-7.4). The highest number of recorded cases was in infants aged 1-12 months (43.4%). Fever (77.6%) and respiratory symptoms (68.8%) were the most common clinical manifestations. A statistically significant association was observed between the presence of fever and the XBB variant (p < 0.015), the presence of upper respiratory symptoms and the XBB variant (p = 0.015), the presence of gastrointestinal symptoms and the Omicron BA.2 variant (p = 0.009), and the presence of laryngitis and the XBB variant (p < 0.001). The highest number of admissions was recorded in patients aged 1-12 months (61/133; 45.9%), followed by school-aged children aged 6-11 years (22/133; 16.5%).

Conclusion: The clinical presentation and age distribution of COVID-19 infections have changed over time. Infants aged 1-12 months were the most affected, a consistent trend across the pandemic. Fever remained the most common clinical manifestation throughout the study period, followed by upper respiratory symptoms.