title: Analysis of Web access logs for surveillance of influenza.
abstract: The purpose of this study was to determine whether the level of influenza in a population correlates with the number of times that internet users access information about influenza on health-related Web sites. We obtained Web access logs from the Healthlink Web site. Web access logs contain information about the user and the information the user accessed, and are maintained electronically by most Web sites, including Healthlink. We developed weekly counts of the number of accesses of selected influenza-related articles on the Healthlink Web site and measured their correlation with traditional influenza surveillance data from the Centers for Disease Control and Prevention (CDC) using the cross-correlation function (CCF). We defined timeliness as the time lag at which the correlation was a maximum. There was a moderately strong correlation between the frequency of influenza-related article accesses and the CDC's traditional surveillance data, but the results on timeliness were inconclusive. With improvements in methods for performing spatial analysis of the data and the continuing increase in Web searching behavior among Americans, Web article access has the potential to become a useful data source for public health early warning systems.
authors.affiliation: RODS Laboratory, Center for Biomedical Informatics, University of Pittsburgh, PA 15219, USA. hjohnson@cbmi.pitt.edu
authors.forename: Heather A
authors.initials: HA
authors.lastname: Johnson
authors.forename: Michael M
authors.initials: MM
authors.lastname: Wagner
authors.forename: William R
authors.initials: WR
authors.lastname: Hogan
authors.forename: Wendy
authors.initials: W
authors.lastname: Chapman
authors.forename: Robert T
authors.initials: RT
authors.lastname: Olszewski
authors.forename: John
authors.initials: J
authors.lastname: Dowling
authors.forename: Gary
authors.initials: G
authors.lastname: Barnas
mesh_terms: D002487:Centers for Disease Control and Prevention, U.S.; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006266:Health Education / Q000706:statistics & numerical data; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D007255:Information Services / Q000706:statistics & numerical data; D020407:Internet / Q000706:statistics & numerical data*; D011159:Population Surveillance / Q000379:methods*; D040442:Public Health Informatics; D014481:United States / Q000453:epidemiology