aCases without detection of bacteria were evaluated as clinically bacterial if they fulfilled one of the following criteria: unilobular or multilobular pulmonary infiltrate or CRP >100 mg/l or PCT >0.25 μg/l or antibiotic therapy before rtPCR and no bacterium detection and biomarkers indeterminate (CRP >100 mg/l and PCT ≤0.25 μg/l or CRP between 51 and 100 mg/l and PCT not available)