Using search patterns to track dengue fever

(Cross-posted on the Google.org Blog)

What does baseball have in common with gazebos? We’re not sure, except that people search on Google for both terms in similar patterns. Last week we introduced Google Correlate, an experimental tool enabling researchers to model real-world behavior using search trends. We’ve heard from many researchers who want to mine this data for new discoveries about economics and public health—much like we designed Google Flu Trends to give an early warning about flu outbreaks. We hope they’re able to make useful discoveries with Google Correlate.

While building Google Correlate, we used it to create an early warning system for another important disease. Google Dengue Trends in Bolivia, Brazil, India, Indonesia and Singapore provides an additional surveillance tool for a disease that affects about 100 million people each year. Dengue is a virus spread through mosquito bites that creates symptoms including high fever, severe headache and pain, rash and mild bleeding. There is no vaccine or treatment, so public health efforts are largely focused on helping people take steps to prevent being infected with the disease.

Singapore has an impressively timely surveillance system for dengue, but in many countries it can take weeks or months for dengue case data to be collected, analyzed and made available. During the dengue outbreak at last year’s Commonwealth Games, we discussed the need for timely dengue information. With help from Professor John Brownstein and Emily Chan from HealthMap, a program at Children’s Hospital Boston and Harvard Medical School, we were able to create our system. Using the dengue case count data provided by Ministries of Health and the World Health Organization, we’re able to build a model that offers near real-time estimates of dengue activity based on the popularity of certain search terms. Google Dengue Trends is automatically updated every day, thereby providing an early indicator of dengue activity.

The methodology for this system is the same as that for Google Flu Trends and is outlined in a newly published article in PLoS Neglected Tropical Diseases.

We hope the early warning provided by Google Dengue Trends helps health officials and the public prepare for potential dengue outbreaks. For those who live in places where dengue is present, remember to follow the advice of health officials to prevent infection by wearing mosquito repellent and emptying any containers that lure mosquito larvae by gathering standing water.

Posted by Vikram Sahai, Software Engineer