We used records from the nationwide hospital discharge system, provided by the Chilean Ministry of Health. These records encompass all hospital admissions in both public (156 hospitals) and private (78 hospitals) institutions and document the main diagnosis (ICD-10 codes) and bed usage during the hospitalization period. Only infants aged 4 years or less are counted. Hospitals that have not reported or have partially reported data as of the update date are also excluded from monitoring.

Data technical norms

In Chile, diagnostic procedures for RSV are conducted comprehensively only at healthcare facilities associated with a nationwide sentinel program, which includes 32 hospitals, mainly using polymerase chain reaction (PCR). Consequently, there is no direct RSV diagnosis available for each hospital admission. We constructed an estimated daily series of RSV-related hospital admissions and bed usage (by type) by filtering hospital admissions with ICD-10 diagnosis codes most likely associated with RSV infection. In summary, considering only admissions at facilities belonging to the sentinel program, and for each week, we extrapolated the proportion of admissions with a positive RSV diagnosis for each set of ICD-10 codes, thus generating an estimated weekly series of positive cases of RSV. Then, we constructed the weekly series of RSV positivity associated with a number of candidate sets of ICD-10 codes and selected the set that best matched the aggregate weekly positivity series of RSV reported by the sentinel program. Finally, we constructed the series related to RSV by filtering inpatient care data from all facilities, including only those records with a main ICD-10 diagnosis within the set of codes selected previously. Diagnostic codes: J121 - J205 - J210 - J219 - B974.