Many critically ill patients with 2009 pandemic influenza A (H1N1) (2009 H1N1) infection were noted to be obese, but whether obesity, rather than its associated co-morbidities, is an independent risk factor for severe infection is unknown. Using public health surveillance data, the authors analyzed demographic and clinical characteristics of California residents hospitalized with 2009 H1N1 infection to assess whether obesity and extreme obesity were an independent risk factor for death among case patients.

Findings: Half of Californians hospitalized with 2009 H1N1 infection were obese. Extreme obesity was associated with increased odds of death. Obese adults with 2009 H1N1 infection should be treated promptly and considered in prioritization of vaccine and antiviral medications during shortages.