BMJ medical innovations: During the swine flu pandemic, Google showed that it was able to track the spread using the searches that its users were making. In this video Dr Patty Kostkova shows her work using twitter - and how the data from that could be used to track future epidemics.
Related blog post from ScienceRoll:
"Do you remember when Google Flu Trends was announced to be able to track and predict flu outbreaks in US states based on the search queries focusing on flu symptoms? Do you remember when a study pointed out although it was interactive and neat but was not as useful as CDC national surveillance programs? Well, now Twitter is meant to fill this gap. If you ask me, it won’t."