Tuesday, May 31, 2011

Google: Tracking Dengue Trends



# 5586



In November of 2008 Google – the 800 lb gorilla of Internet search engines – announced the opening of their Flu Tracking website (see Google Unveils Flu Tracking System).


The idea was intriguingly simple, really. 


Since people tend to perform internet searches on health topics of concern, it stood to reason that more people would Google `flu’ or `influenza’ when the flu was circulating in their communities.


By tracking the number of searches of flu-related terms by geographical region – and comparing them to baselines established over a period of years – it should be possible to get an early warning of influenza-like illness (ILI) activity.


The rub, of course, is that not all ILIs are the flu.


In October of 2009, during the height of the fall wave of the H1N1 pandemic, I posted the following graphic on my blog.




Of the more than 10,000 samples submitted for testing during the 1st week of October 2009, more than 72%almost 3/4ths –  came back negative for influenza.


About a year ago a researchers at the University of Washington found that Google Flu Trends was somewhat less accurate than the CDC in predicting laboratory confirmed influenza, but was a robust tool for detecting less specific influenza-like illnesses.


While separating influenza from other ILIs remains a challenge, and intense media attention can spur search spikes and skew results, the data being provided by Google’s Flu Trends has proven to be both timely and valuable.


Since the early results from Flu Trends has proved so promising, Google is now setting their sights on the fastest growing mosquito-borne illness in the world; Dengue.


As with influenza-like illnesses, aggregated search totals for Dengue in a number of countries correspond closely with outbreaks. Below you’ll see the correlation between Dengue activity and Dengue-related queries in Brazil since 2003.




The Dengue Trends project is small right now, with just 5 countries being tracked (Bolivia, Brazil, India, Indonesia, and Singapore). 


Not all dengue-endemic countries have enough detailed historical dengue surveillance and enough Internet access and activity to monitor right now, but more countries are expected to be added over time.


This is what the Dengue Trends front page looks like. 




Google provides this service, and data, free of charge and as a public service. 


They also continue to release a number of free data mining tools, including one last week called Google Correlate that works like Google Trends in reverse.


Rather than inputting a search term and seeing the trend, Google Correlate allows you to upload your own data series, and see what search terms are a trending match. 


For more on how all of this works, check out the Google Labs announcement.  Statistical data geeks will find a White Paper on all of this, but for those of us who are arithmetically challenged, Google was kind enough to present the basics in the form of an 8-page comic book.





Google Flu Trends and Dengue Trends won’t supplant traditional surveillance systems, of course.


But they can serve as a novel and innovative real-time adjunct to conventional surveillance systems, and over time will likely improve in both geographic coverage and accuracy.


It should be fascinating to watch them evolve.