Serum cytokine levels over time (3 days after admission and antiviral treatment) showed a decrease of IL-6, IP-10, TNFα, IFNγ and IL-17 in critical patients with nvA (H1N1)-ARDS (Table 4 ). Serum cytokine levels over time in nvA(H1N1)-ARDS survivors showed a significant decrease of IL-6, IP-10 and TNFα (Table 5 ). In nonsurvivors versus survivors from the nvA(H1N1)-ARDS group, the levels of IL-6 and IL-15 on admission and 3 days after were significantly higher ( Table 6 ). IL-17 was higher in nonsurvivors 3 days after admission (Table 6) . Correlation between cytokine levels and clinical or laboratory characteristics in patients with confirmed nvA(H1N1) infection was determined by Spearman correlation coefficient. We found significant correlation of IL-6, IL-8 and IL-15 levels with C-reactive protein (r = 0.67, P < 0.001; r = 0.5, P = 0.003; and r = 0.48, P = 0.005, respectively), with PaO 2 :FiO 2 ratio (r = -0.556, P = 0.001; r = -0.574, P < 0.001; and r = -0.614, P < 0.001, respectively) and with interval between symptom onset and hospital admission (r = 0.51, P = 0.002; r = 0.41, P = 0.019; and r = 0.48, P = 0.004, respectively).