McIver, David J. and John S. Brownstein (April 17, 2014) "Wikipedia Usage Estimates Prevalence of Influenza-Like Illness in the United States in Near Real-Time" PLOS Computational Biology: http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003581

"Wikipedia article view data has been demonstrated to be effective at estimating the level of Influenza-Like Illness [ILI] activity in the US, when compared to CDC data.... and can provide a reliable estimate of ILI activity up to 2 weeks in advance of traditional ILI reporting."