Bermejo-Martin et al. reported increased serum levels of IL-6, IFN-γ, and tumor necrosis factor-α in patients with pandemic (H1N1) 2009 during the fi rst 5 days after symptom onset; no difference in levels of these 3 cytokines was observed in patients with mild disease and controls (5) . However, similar to another report (4), we detected increases of IL-6 and IFN-γ levels in patients with mild disease during the fi rst 3 days after symptom onset. These different patterns may be caused by different intervals from time of symptom onset to date of sample collection (5 days vs. 3 days) because IL-6 and IFN-γ levels in our study quickly decreased to baseline levels ≤7 days after symptom onset. These results suggest that serum IL-6 and IFN-γ , and IL-6 are medians (pg/mL). Serum HAI antibody titers were transformed by using the natural logarithm and are shown as means. Baseline cytokine concentrations on the y-axis are values for healthy persons. *p<0.05 when IL-6 or HAI antibody levels were compared with those at day 5; †p<0.05 when IL-10 level was compared with those at baseline; ‡p<0.05 when IL-10 level was compared with those at days 5 or 15; §p<0.05 when value was compared with that at any other time point; ¶p<0.05 when value was compared with those at days 5, 15, or 49. levels may be increased in patients with pandemic (H1N1) 2009 within the fi rst 3 days after symptom onset, followed by a decrease to baseline levels ≤5 days after symptom onset in patients with mild disease or a continuous increase in severely affected patients. IL-6 and IFN-γ are associated with antiviral immune responses during infl uenza infection (6) (7) (8) . However, continuous, excessive release of IL-6 three days after illness onset likely contributed to serious pulmonary infl ammation and tissue injury, as has been documented for severe acute respiratory syndrome and 1918 pandemic infl uenza, but this release could be tempered by production of IL-10 (6, 7, (9) (10) (11) .