In agreement with the findings of some studies [20, 22, 34] and in contrast to others [7, 29, 39], this study failed to identify specific predictors of viral detection in multivariate logistic regression. Advancing age was previously described as more common in viral infections [19, 22, 29, 35] but the evidence is inconclusive [31, 32]. In this study, younger age was a significant predictor of virus detection in univariable logistic regression if all patients were considered, but not in stratified analyses in children and adults. The mean age in the group with respiratory viral infections was lower than in the remaining patients (29 vs. 47 years; p < 0.001) but the differences were not significant if stratified for children and adults.