title: A novel risk factor for a novel virus: obesity and 2009 pandemic influenza A (H1N1).
abstract: BACKGROUND
  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.
  
  
  METHODS
  using public health surveillance data, we analyzed demographic and clinical characteristics of California residents hospitalized with 2009 H1N1 infection to assess whether obesity (body mass index [BMI] ≥ 30) and extreme obesity (BMI ≥ 40) were an independent risk factor for death among case patients ≥ 20 years old.
  
  
  RESULTS
  during the period 20 April-11 August 2009, 534 adult case patients with 2009 H1N1 infection for whom BMI information was available were observed. Two hundred twenty-eight patients (43%) were ≥ 50 years of age, and 378 (72%) had influenza-related high-risk conditions recognized by the Advisory Committee on Immunization Practices as risk factors for severe influenza. Two hundred and seventy-four (51%) had BMI ≥ 30, which is 2.2 times the prevalence of obesity among California adults (23%) and 1.5 times the prevalence among the general population of the United States (33%). Of the 92 case patients who died (17%), 56 (61%) had BMI ≥ 30 and 28 (30%) had BMI ≥ 40. In multivariate analysis, BMI ≥ 40 (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.4-5.9) and BMI ≥ 45 (OR, 4.2; 95% CI, 1.9-9.4), age ≥ 50 years (OR, 2.1; 95% CI, 1.2-3.7), miscellaneous immunosuppressive conditions (OR, 3.9; 95% CI, 1.6-9.5), and asthma (OR, 0.5; 95% CI, 0.3-0.9) were associated with death.
  
  
  CONCLUSIONS
  half of Californians ≥ 20 years of age 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.
authors.affiliation: Division of Communicable Disease Control, California Department of Public Health, Richmond, California94804, USA. janice.louie@cdph.ca.gov
authors.forename: Janice K
authors.initials: JK
authors.lastname: Louie
authors.forename: Meileen
authors.initials: M
authors.lastname: Acosta
authors.forename: Michael C
authors.initials: MC
authors.lastname: Samuel
authors.forename: Robert
authors.initials: R
authors.lastname: Schechter
authors.forename: Duc J
authors.initials: DJ
authors.lastname: Vugia
authors.forename: Kathleen
authors.initials: K
authors.lastname: Harriman
authors.forename: Bela T
authors.initials: BT
authors.lastname: Matyas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002140:California / Q000453:epidemiology; D016638:Critical Illness; D005260:Female; D006760:Hospitalization; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality* / Q000821:virology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D012307:Risk Factors