Finelli L: Influenza-associated pneumonia among hospitalized patients with 2009 pandemic influenza Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or co

Background. Pneumonia was a common complication among hospitalized patients with 2009 pandemic influenza A H1N1 [pH1N1] in the United States in 2009. Methods. Through 2 national case series conducted during spring and fall of 2009, medical records were reviewed. A pneumonia case was defined as a hospitalized person with laboratory-confirmed pH1N1 virus and a chest radiographic report consistent with pneumonia based on agreement among 3 physicians. Results. Of 451 patients with chest radiographs performed, 195 (43%) had pneumonia (spring, 106 of 237 [45%]; fall, 89 of 214 [42%]). Compared with 256 patients without pneumonia, these 195 patients with pneumonia were more likely to be admitted to the intensive care unit (52 % vs 16%), have acute respiratory distress syndrome (ARDS; 26 % vs 2%), have sepsis (18 % vs 3%), and die (17 % vs 2%; P,.0001). One hundred eighteen (61%) of the patients with pneumonia had $1 underlying condition. Bacterial infections were reported in 13 patients with pneumonia and 2 patients without pneumonia. Patients with pneumonia, when compared with patients without pneumonia, were equally likely to receive influenza antiviral agents (78 % vs 79%) but less likely to receive antiviral agents within #2 days of illness onset (28 % vs 50%; P,.0001). Conclusions. Hospitalized patients with pH1N1 and pneumonia were at risk for severe outcomes including ARDS, sepsis, and death; antiviral treatment was often delayed. In the absence of accurate pneumonia diagnostics