Sentinel surveillance of acute respiratory infection (ARI) in children under five years old from 2015 to 2022 at a high-complexity health care institution in Cali, Colombia.

Background: Respiratory viral infections in children under five pose a significant public health challenge worldwide. Sentinel surveillance systems identify viral causes of acute respiratory infections (ARIs), providing real-time data to enhance public health strategies. This study analyses data from 2015-2022 from one of Colombia's principal sentinel surveillance centres for severe acute respiratory infection (SARI), located in a high-complexity hospital in the Pacific region. While findings reflect a specific local context, they offer valuable insights into viral circulation in a high burden setting and contribute to strengthening national and global surveillance efforts. Methods: A cross-sectional study was conducted, tracking cases from epidemiological week 1 of 2015 to week 52 of 2022. Viral identification and clinical outcomes were analysed, focusing on intensive care unit (ICU) admissions and associated risk factors. Results: A total of 3035 cases of respiratory viral infections were analysed from a sentinel hospital between 2015 and 2022. The median age of children was 12 months. Respiratory syncytial virus (RSV) was the most common pathogen (30.9%), followed by influenza (6.7%) and adenovirus (5.1%). Intensive care unit admission rates were higher among children with underlying conditions such as cardiovascular disease and malnutrition (33%). RSV accounted for 33% of ICU cases. Infection rates peaked seasonally, particularly in children under 12 months. Younger age and comorbidities were key risk factors for ICU admission. Conversely, older children and those infected with RSV or influenza had lower ICU admission rates. Conclusions: Sentinel surveillance data confirm the high burden of RSV and other respiratory viruses in children, particularly those under 12 months and with comorbidities. Findings highlight the need for targeted public health measures, including improved vaccination and health care access for high-risk groups. Strengthening surveillance is essential for timely, evidence-based interventions.