From the New England Journal of Medicine we have this review of digitally-enabled public health surveillance.  The recent online activity over the swine flu and Google Flu Trends are only the latest efforts in activity that go back 15 years.  What started with reporting systems has grown to include news aggregation, mashups, and, yes, even the Internet darling of the moment, Twitter.  The authors are concerned, however, that the increasing online capacity for assessment and analysis not displace the work of public health practitioners and clinics.  Put another way, its fine to look up symptoms online, but you should still see a doctor if needed rather than self-diagnosing.  There are other concerns:

Information overload, false reports, lack of specificity of signals, and sensitivity to external forces such as media interest may limit the realization of their potential for public health practice and clinical decision making. Sources such as analyses of search-term use and news media may also face difficulties with verification and follow-up. Though they hold promise, these new technologies require careful evaluation. Ultimately, the Internet provides a powerful communications channel, but it is health care professionals and the public who will best determine how to use this channel for surveillance, prevention, and control of emerging diseases.

Given the title of the NEJM piece – “Digital Disease Detection – Harnessing the Web for Public Health Surveillance” – I think another pair of concerns to add is privacy and security.  If IP addresses can be tracked, which is true with some of these cases, then it is possible to connect particular incidents to particular individuals.  Unless its necessary to communicate with specific individuals, measures should be taken to preserve the anonymity of those whose information supports this public health monitoring.  The security of the databases and other systems using this information need to be strong enough to guard against breaches and inadvertent exposure.