SP-D is associated with clinical severity only in PICFLU pediatric influenza virus-infected patients without bacterial co-infection. Panels A-E: Influenza-infected children without bacterial co-infection (n=45, 1 death); Panels F-J: Influenza-bacterial co-infection (n=49, 5 deaths). PRISM III admission disease severity score (4A, 4F) and acute respiratory distress syndrome (ARDS) (4B, 4G). Outcomes include days of mechanical ventilator support in survivors (4C, 4H), hospital length of stay (LOS) in hours (4D, 4I), pediatric intensive care unit (ICU) hours (4E, 4J), Spearman correlation (r) and p values from unpaired t tests are indicated.