Influenza surveillance within hospitals: what is the world doing?

Influenza within hospitals is receiving increasing attention as a result of planning for an influenza pandemic and the magnitude and severity of the 2007 influenza season in Australia. This article reviews current approaches to influenza surveillance of admitted patients, as opposed to surveillance of emergency departments, in hospitals internationally. Most examples came from the United States of America and Canada, although systems have been described in the United Kingdom and Japan. In-hospital surveillance of influenza occurs within broader surveillance systems established by national governments, and through other systems established by sub-national governments and individual hospitals. Systems vary in focus, i.e. laboratory confirmed influenza or influenza-like illness, and some are labour intensive while others incorporate differing degrees of automation. The approach to influenza surveillance within hospitals will depend on objectives and available resources, although an automated approach is likely to have greater longevity as labour requirements are reduced.