HMGB1 and viral infectious disease: Serum HMGB1 levels were analyzed at 0, 4, 6, 8, 10, and 14 days p.i. As shown for influenza B virus infection (Fig. 1A), California pH1N1 virus infection induced a similar temporal pattern of HMGB1 release in serum, with a gradual increase over days 0 to 4 p.i., reaching peak concentrations at days 6 to 8 p.i., and finally declining by days 10 to 14 p.i.