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.

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.