Hospital burden of severe acute respiratory infections associated with influenza in sentinel surveillance units in the Republic of Serbia: Season 2025/2026

Sentinel hospital-based surveillance of severe acute respiratory infections (SARIs) enables assessment of the hospital burden of influenza and monitoring of severe clinical outcomes. The aim of this work is to estimate the hospital burden of SARI and SARI cases associated with influenza within the sentinel network of the Republic of Serbia during the 2025/2026 season. A descriptive analysis of aggregated weekly data from 11 sentinel hospital units in four statistical regions of Serbia was conducted for the period from the 40th epidemiological week of 2025 to the 20th epidemiological week of 2026. SARI hospitalizations, testing coverage and flu positivity, intensive care unit (ICU) treatment, mortality, and temporal distribution of hospital workload were analyzed. The estimated number of influenza-related SARI hospitalizations was calculated by applying the percentage of positivity among tested SARI cases to the total number of registered SARI cases. A total of 2,584 (7.3%) SARI cases were registered among 35,361 newly admitted patients. A total of 2,275 (88.0%) cases were tested, of which 423 (18.6%) were positive for influenza. The highest burden was recorded in persons aged ≥65 years. In the ICU, 17.2% of SARI and 18.0% of influenza-positive SARI cases were treated, with deaths in 4.6% and 6.6%, respectively. The hospital load reached its maximum in the 1st epidemiological week of 2026. Sentinel SARI surveillance enables assessment of hospital burden of influenza and severe clinical outcomes, with a particularly pronounced burden among the elderly.