von Baum H, Schweiger B et al. (2010): How deadly is seasonal influenza associated pneumonia? The German Competence Network for Community-acquired pneumonia (CAPNETZ)
Eur. Resp. J.: Epub Sep 3.

The emergence of new influenza virus subtypes has rekindled the interest in the clinical course and outcome of patients with influenza-associated pneumonia. Based on prospective data from 5032 patients with CAP included in the German CAP-Competence Network (CAPNETZ), we studied the incidence, clinical characteristics, and outcome of patients with influenza-associated CAP and compared these to patients without influenza. Diagnosis relied on a positive PCR for influenza in throat washings. 160 patients with influenza-associated CAP were identified (3,2% of total population, 12% of those with defined etiology). 34 patients (21%) with seasonal influenza had a concomitant pathogen (mostly S. pneumoniae). Patients with influenza associated CAP were significantly older, had been less often vaccinated, and had less often preceding antibacterial treatment. Thirty-day mortality was low (4.4%), not different to that of patients with pneumonia caused by bacterial (6.2%) or viral other than influenza pathogen (4%). Patients with influenza plus a bacterial pathogen (mixed influenza-associated pneumonia) had a higher mortality than those with pure influenza associated pneumonia (9% vs 3.2%). Mortality was higher in patients with mixed as compared to pure influenza associated pneumonia. However, we could not observe any excess mortality in patients with influenza associated pneumonia.