title: Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity.
abstract: BACKGROUND
  To augment established influenza surveillance systems in the United States, the Centers for Disease Control and Prevention and the Council of State and Territorial Epidemiologists implemented the Aggregate Hospitalization and Death Reporting Activity (AHDRA) in August 2009. The AHDRA was designed to meet increased demands for timely and detailed information describing illness severity during the 2009 H1N1 influenza A (pH1N1) pandemic response.
  
  
  OBJECTIVE
  We describe the implementation of AHDRA and provide preliminary results from this new surveillance activity.
  
  
  METHODS
  All 50 US states were asked to report influenza-associated hospitalizations and deaths to AHDRA each week using either a laboratory-confirmed or syndromic surveillance definition. Aggregate counts were used to calculate age-specific weekly and cumulative rates per 100,000, and laboratory-confirmed reports were used to estimate the age distribution of pH1N1 influenza-associated hospitalizations and deaths.
  
  
  RESULTS
  From August 30, 2009, through April 6, 2010, AHDRA identified 41,689 laboratory-confirmed influenza-associated hospitalizations and 2096 laboratory-confirmed influenza-associated deaths. Aggregate Hospitalization and Death Reporting Activity rates peaked earlier than hospitalization and death rates seen in previous influenza seasons with other surveillance systems, and the age distribution of cases revealed a tendency for hospitalizations and deaths to occur in persons <65 years for age.
  
  
  CONCLUSIONS
  Aggregate Hospitalization and Death Reporting Activity laboratory-confirmed reports provided important information during the 2009 pandemic response. Aggregate Hospitalization and Death Reporting Activity syndromic reports were marked by low representativeness and specificity and were therefore less useful. The AHDRA was implemented quickly and may be a useful surveillance system to monitor severe illness during future influenza pandemics.
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA. mjhung@cdc.gov
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jhung
authors.forename: Heidi
authors.initials: H
authors.lastname: Davidson
authors.forename: Anne
authors.initials: A
authors.lastname: McIntyre
authors.forename: William J
authors.initials: WJ
authors.lastname: Gregg
authors.forename: Sharoda
authors.initials: S
authors.lastname: Dasgupta
authors.forename: Tiffany
authors.initials: T
authors.lastname: D'Mello
authors.forename: Victoria
authors.initials: V
authors.lastname: White
authors.forename: Ashley
authors.initials: A
authors.lastname: Fowlkes
authors.forename: Lynnette
authors.initials: L
authors.lastname: Brammer
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002487:Centers for Disease Control and Prevention, U.S. / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D018563:Disease Notification / Q000379:methods*; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality* / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D011159:Population Surveillance / Q000379:methods*; D014481:United States / Q000453:epidemiology; D055815:Young Adult