Plasma cytokine/chemokine concentrations in adults hospitalized for seasonal or pandemic H1N1 influenza, measured at presentation.

Values are stated as median (interquartile range, IQR); pandemic influenza A/H1N1 ‘severe’: radiographic pneumonia plus hypoxemia; ‘mild’: hospitalized for significant respiratory or systemic symptoms (only 5/29 patients had mild pulmonary infiltrates on chest radiographs)[8]. Over 80% of seasonal influenza patients had respiratory/cardiovascular complications, and nearly half developed hypoxemia. Only 2 patients received long-term immunosuppressants in these cohorts. The normal plasma reference ranges of cytokines/chemokines were obtained from >100 healthy individuals [8], [15].Comparisons: (1) Seasonal influenza A (combined) vs influenza B; (2) seasonal influenza A/H3N2 vs A/H1N1; (3) severe pH1N1 vs all seasonal influenza cases (similar results when influenza B was excluded); (4) pH1N1 cases, ‘severe’ vs ‘mild’. Fewer pH1N1 infections had detectable levels of IFN-γ compared with seasonal influenza (8.8% vs 43.4%; p**p≤0.01,*p#p