Case-based surveillance of influenza hospitalizations during 2004-2008, Colorado, USA

Emerg Infect Dis. 2009 Jun;15(6):892-8. doi: 10.3201/eid1506.081645.


Colorado became the first state to make laboratory-confirmed influenza-associated hospitalizations a case-based reportable condition in 2004. We summarized surveillance for influenza hospitalizations in Colorado during the first 4 recorded influenza seasons (2004-2008). We highlight the similarities and differences among influenza seasons; no 2 seasons were entirely the same. The 2005-06 influenza season had 2 distinct waves of activity (types A and B), the 2006-07 season was substantially later and milder, and 2007-08 had substantially greater influenza B activity. The case-based surveillance for influenza hospitalizations provides information regarding the time course of seasonal influenza activity, reported case numbers and population-based rates by age group and influenza virus type, and a measure of relative severity. Influenza hospitalization surveillance provides more information about seasonal influenza activity than any other surveillance measure (e.g., surveillance for influenza-like illness) currently in widespread use among states. More states should consider implementing case-based surveillance for influenza hospitalizations.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Aged, 80 and over
  • Child
  • Child, Preschool
  • Clinical Laboratory Techniques
  • Colorado / epidemiology
  • Disease Notification / methods
  • Disease Notification / statistics & numerical data*
  • Hospitalization / statistics & numerical data*
  • Humans
  • Infant
  • Infant, Newborn
  • Influenza A virus / isolation & purification
  • Influenza B virus / isolation & purification
  • Influenza, Human / diagnosis
  • Influenza, Human / epidemiology*
  • Influenza, Human / virology
  • Laboratories, Hospital
  • Middle Aged
  • Population Surveillance / methods*
  • Seasons
  • Young Adult