Flutracking surveillance: comparing 2007 New South Wales results with laboratory confirmed influenza notifications

General practice and hospital surveillance for influenza-like illness (ILI) and laboratory influenza surveillance provide useful but incomplete information on influenza incidence. Flutracking is an Australian pilot of an Internet-based community ILI syndromic surveillance system designed to detect inter-pandemic and, potentially, pandemic influenza. Presence of fever and/or cough and absence from normal duties are collected weekly. Influenza vaccination status of respondents is recorded. New South Wales Flutracking data for 2007 were compared with New South Wales laboratory notifications for confirmed influenza to validate it's ability to provide alerts of influenza activity. Symptom rates amongst vaccinated and unvaccinated Flutracking respondents were compared using a variety of case definitions, with New South Wales laboratory influenza notifications. Time series methods were used to estimate the degree of correlation between each Flutracking case definition and the laboratory data. For the unvaccinated group, the correlations between all Flutracking case definitions and laboratory data were statistically significant, while for the vaccinated group no case definitions were significantly correlated with laboratory data. Thus Flutracking ILI data amongst unvaccinated participants correlated well with influenza laboratory surveillance.