Rise of Lower Respiratory Tract Infections Other than Respiratory Syncytial Virus in the Emergency Room: Results from the Season (2024/25) of the RISE Study

Acute respiratory infections (ARI) are a major cause of pediatric emergency department (ED) visits and hospitalizations. Although respiratory syncytial virus (RSV), influenza, and rhinovirus (RV) are common etiological agents, pathogen-specific data from pediatric emergency settings remain limited. This prospective surveillance study quantified ARI-related ED visits, described pathogen-specific epidemiology, and assessed attendance and hospitalization rates as well as the distribution of lower versus upper respiratory tract infections (LRTI/URTI) in children younger than 60 months in two pediatric EDs in Berlin between November 1, 2024 and May 31, 2025. Respiratory pathogens were identified using nasopharyngeal swab samples tested by multiplex real-time RT-PCR (QIAstat-Dx ® Respiratory Panel Plus). Within the study period 4042 ARI-related ED visits occurred. A total of 310 children were enrolled in our study (median age 18 months); 115 (37.1%) had LRTI and 195 (62.9%) URTI. At least one respiratory pathogen was detected in 271 children (87.4%). The attendance rate for RSV was 24.4% (66 cases), for FLU 25.8% (70 cases), and for RV 29.5% (80 cases). Overall, 93 children (30.0%) were hospitalized, including 65 with LRTI and 28 with URTI. Hospitalization rates were highest for RSV infections (26/65, 40.0%) and RV infections (28/65, 43.1%), and lower for FLU infections (13/69, 18.8%). Hospitalization due to LRTI predominated among children with RSV (24/26, 92.3%) and RV infections (20/28, 71.4%), whereas FLU infections were less frequently observed (7/13, 53.9%). Furthermore, younger age, a history of pneumonia, a history of bronchiolitis, and the absence of breastfeeding were associated with hospitalization. In contrast to the previous season, in which RSV was associated with the highest attendance and hospitalization rate, we observed a high burden of RV infections in the 2024/2025 season. These findings may impact surveillance strategies, clinical management, and future public health strategies.