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."