Risk of influenza-like illness in an acute health care setting during community influenza epidemics in 2004-2005, 2005-2006, and 2006-2007: a prospective study

Arch Intern Med. 2011 Jan 24;171(2):151-7. doi: 10.1001/archinternmed.2010.500.


Background: The person-to-person transmission of influenza-like illness (ILI) and influenza has been described mostly in long-term care units. Studies in acute hospital settings are rare and mostly retrospective.

Methods: We prospectively estimated the relative risk (RR) of hospital-acquired (HA) ILI during hospitalization according to in-hospital exposures to contagious individuals. Surveillance of ILI and laboratory-confirmed influenza was undertaken at Edouard Herriot Hospital (1100 beds) during 3 influenza seasons. A total of 21 519 patients and 2153 health care workers (HCWs) from 2004 to 2007 were included. The RR of HA-ILI in patients was calculated according to exposure to other contagious patients and HCWs.

Results: For patients exposed to at least 1 contagious HCW compared with those with no documented exposure in the hospital, the RR of HA-ILI was 5.48 (95% confidence interval [CI], 2.09-14.37); for patients exposed to at least 1 contagious patient, the RR was 17.96 (95% CI, 10.07-32.03); and for patients exposed to at least 1 contagious patient and 1 contagious HCW, the RR was 34.75 (95% CI, 17.70-68.25).

Conclusions: Hospitalized patients exposed to potentially infectious patients and HCWs with ILI inside the hospital are at greater risk for HA-ILI. Such results identify priorities regarding preventive measures for seasonal or pandemic influenza.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Disease
  • Adult
  • Aged
  • Aged, 80 and over
  • Cross Infection / epidemiology*
  • Cross Infection / transmission
  • Epidemics / statistics & numerical data*
  • Female
  • Humans
  • Influenza, Human / epidemiology*
  • Influenza, Human / transmission
  • Male
  • Middle Aged
  • Prospective Studies
  • Residence Characteristics / statistics & numerical data*
  • Risk