title: Disparities in the severity of influenza illness: a descriptive study of hospitalized and nonhospitalized novel H1N1 influenza-positive patients in New York City: 2009-2010 influenza season.
abstract: OBJECTIVE
  To investigate the association between socioeconomic status (SES) and hospitalization for 2009 H1N1 influenza, independently of access to care and known risk factors for severe influenza illness, among New York City residents during the 2009-2010 influenza season.
  
  
  METHODS
  We used a 1:2 case-control study design, matching by age group and month of diagnosis. Cases were defined as laboratory-confirmed patients with 2009 H1N1 influenza who were hospitalized during their illness. Controls were defined as nonhospitalized laboratory-confirmed influenza A patients. Participants were contacted for a telephone interview to collect relevant clinical and demographic data. We used conditional logistic regression to analyze the association between SES and hospitalization.
  
  
  METHODS
  New York City.
  
  
  METHODS
  Of the 171 hospitalized cases who were identified between October 2009 and February 2010, a total of 128 completed telephone interviews. A total of 640 nonhospitalized controls were contacted, and of these, 337 completed interviews.
  
  
  METHODS
  The main outcome of interest was whether or not a patient was hospitalized during his or her 2009 H1N1 influenza illness. Socioeconomic status was measured using education and neighborhood poverty.
  
  
  RESULTS
  We identified a gradient in the odds of hospitalization for 2009 H1N1 influenza by education level among adults. This association could not be entirely explained by access to care and underlying risk factors. An inverse association between odds of hospitalization and neighborhood poverty was also identified among adults and children.
  
  
  CONCLUSIONS
  This study suggests that individuals of lower SES were more vulnerable to severe illness during the 2009 H1N1 pandemic. Additional research is needed to help guide interventions to protect this population during future influenza pandemics.
authors.affiliation: New York City Department of Health and Mental Hygiene, Bureau of Communicable Disease, Queens, NY 11101, USA.
authors.forename: Natalie S
authors.initials: NS
authors.lastname: Levy
authors.forename: Trang Quyen
authors.initials: TQ
authors.lastname: Nguyen
authors.forename: Emily
authors.initials: E
authors.lastname: Westheimer
authors.forename: Marcelle
authors.initials: M
authors.lastname: Layton
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D004196:Disease Outbreaks; D005260:Female; D006297:Health Services Accessibility; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009519:New York City / Q000453:epidemiology; D012307:Risk Factors; D012720:Severity of Illness Index; D012959:Socioeconomic Factors; D055815:Young Adult