How does this work?

We've found that certain search terms are good indicators of dengue activity. Google Dengue Trends uses aggregated Google search data to estimate current dengue activity around the world in near real-time.

Each week, millions of users around the world search for health information online. As you might expect, there are more flu-related searches during flu season, more allergy-related searches during allergy season, and more sunburn-related searches during the summer. You can explore all of these phenomena using Google Insights for Search. But can search query trends provide the basis for an accurate, reliable model of real-world phenomena? In November 2008 we launched Google Flu Trends based on our finding that aggregated search query trends can provide accurate estimates of flu. The journal Nature published our results and methodology.

We have also found a close relationship between how many people search for dengue-related topics and how many people actually have dengue symptoms. Of course, not every person who searches for "dengue" is actually sick, but a pattern emerges when all the dengue-related search queries are added together. We compared our query counts with traditional dengue surveillance systems and found that many search queries tend to be popular exactly when dengue season is happening. By counting how often we see these search queries, we can estimate how much dengue is circulating in different countries and regions around the world.

Historical activity

See data for: 
Brazil Dengue Activity
Dengue activity  Google Dengue Trends estimate  Brazil data

Brazil: Dengue data provided publicly by the Ministry of Health.

These graphs show historical query-based dengue estimates for different countries and regions compared against official dengue surveillance data. As you can see, estimates based on Google search queries about dengue are very closely matched to traditional dengue activity indicators. Of course, past performance is no guarantee of future results. Our system is still new, but we hope to see similar correlations in the coming years.

So why bother with estimates from aggregated search queries? Traditional dengue surveillance is very important, but most health agencies focus on a single country or region and only update their estimates once per week, month or even year. Google Dengue Trends is currently available for a number of countries around the world and is updated every day, providing a complement to these existing systems.

For epidemiologists, this is an exciting development, because early detection of a disease outbreak can reduce the number of people affected. Our up-to-date dengue estimates may enable public health officials and health professionals to better respond to seasonal outbreaks.

Learn more about the research behind Google Dengue Trends:

Read the article published by PLoS, Neglected Tropical Diseases, Using Web Search Query Data to Monitor Dengue Epidemics

Download the Google Dengue Trends estimates for the world

Protecting User Privacy

At Google, we are keenly aware of the trust our users place in us, and of our responsibility to protect their privacy. Google Dengue Trends can never be used to identify individual users because we rely on anonymized, aggregated counts of how often certain search queries occur each week. We rely on millions of search queries issued to Google over time, and the patterns we observe in the data are only meaningful across large populations of Google search users. You can learn more about how this data is used and how Google protects users' privacy at our Privacy Center.