Objectives: The detection of respiratory syncytial virus (RSV) in upper airway samples does not necessarily infer causality of illness. We aimed to calculate the attributable fraction (AF) of RSV in clinical syndromes across age groups. Methods: Using unconditional logistic regression models, we estimated the AF of RSV-associated influenza-like illness (ILI) and severe acute respiratory illness (SARI) cases by comparing RSV detection prevalence among ILI and SARI cases to those of healthy controls in South Africa, 2012-2016. The analysis, stratified by HIV serostatus, was conducted in the age categories