Factors Associated With Death or Hospitalization Due to Pandemic 2009 Influenza A(H1N1) Infection in California

CONTEXT Pandemic influenza A(H1N1) emerged rapidly in California in April 2009. Preliminary comparisons with seasonal influenza suggest that pandemic 2009 influenza A(H1N1) disproportionately affects younger ages and causes generally mild disease. OBJECTIVE To describe the clinical and epidemiologic features of pandemic 2009 influenza A(H1N1) cases that led to hospitalization or death. DESIGN, SETTING, AND PARTICIPANTS Statewide enhanced public health surveillance of California residents who were hospitalized or died with laboratory evidence of pandemic 2009 influenza A(H1N1) infection reported to the California Department of Public Health between April 23 and August 11, 2009. MAIN OUTCOME MEASURE Characteristics of hospitalized and fatal cases. RESULTS During the study period there were 1088 cases of hospitalization or death due to pandemic 2009 influenza A(H1N1) infection reported in California. The median age was 27 years (range,