Google Flu Trends - FAQ Frequently asked questions

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About Google Flu Trends

What information is provided by Google Flu Trends?
Google Flu Trends provides up-to-date estimates of flu activity in Australia, New Zealand, and the United States based on aggregated search queries. Data can be viewed on the Flu Trends website or downloaded as a CSV file for analysis.

What information is provided by Experimental Flu Trends for Mexico?
Experimental Flu Trends for Mexico provides up-to-date estimates of possible flu activity based on aggregated search queries. Unlike Google Flu Trends, these estimates have not been verified against historical Mexican flu data. This experimental data can be viewed on the website or downloaded as a CSV file for analysis.

I'm a public health official. How can I get Google Flu Trends for my country?
Thanks for your interest! If your country experiences seasonal influenza and has data on influenza-like illness (ILI), acute respiratory infection (ARI), and/or laboratory-confirmed influenza case counts from the past 3-5 years, we'd like to validate Google Flu Trends for your country. Please contact us for more information.


How does it work?
Google researchers have found a close relationship between how many people search for flu-related topics and how many people actually have flu symptoms. Some search queries tend to be popular exactly when flu season is happening, and are therefore good indicators of flu activity. By training models over multiple seasons we're able to filter and control for news driven terms that may be popular one year, but not the next. Google Flu Trends uses aggregated Google search data to estimate the current flu activity level in different countries around the world, providing a multi-national, up-to-date flu tracking system.

Unlike Google Flu Trends, Experimental Flu Trends for Mexico has not been validated against historic flu data. Read more about how Google Flu Trends works.

How are the flu activity levels determined?
For each country or region where we have access to historical flu data, Flu Trends compares the estimates based on search data against a historical baseline level of flu activity for that area. Depending on whether the current estimate is higher or lower than the baseline, Flu Trends reports the general activity level as Minimal, Low, Moderate, High, or Intense. Each category has a corresponding color that is displayed under the graph.

For Mexico, in the absence of data to provide a historic baseline of flu activity, Flu Trends uses the same scale based on a relative measure of search activity.

How accurate and up-to-date is the information provided by Google Flu Trends?
Historically, national and regional estimates have been very consistent with traditional surveillance data collected by health agencies. Estimates for individual states in the U.S. have not been compared against traditional surveillance data because such data is not publicly available. Because Flu Trends is still new, it's quite possible that future estimates may deviate from actual flu activity, but we're hoping to see similar correlations in the coming years. Flu Trends is still quite experimental for Mexico, as it has not been verified against historic flu data from Mexico.

How is Google Flu Trends useful for pandemic flu?
Google Flu Trends models are built based on historic flu surveillance data. When a new flu virus causes the same symptoms as seasonal flu, Google Flu Trends can detect if overall flu rates are significantly increasing. Some search queries tend to be popular exactly when flu is happening, and are therefore good indicators of flu activity.

How is information gathered to determine countries, regions and states?
Google Flu Trends uses IP address information from our server logs to make a best guess about where queries originated.

For which countries does Google Flu Trends provide estimates?
Anyone connected to the internet can access Google Flu Trends, but we currently have verified estimates for Australia, New Zealand and the United States, and unverified estimates for Mexico. We hope to produce estimates for other countries in the future.

What organizations provided flu data for each country?

* Australia: Data provided publicly by the Victorian Infectious Diseases Reference Laboratory.
* New Zealand: Data provided courtesy of the WHO National Influenza Centre at the Institute of Environmental Science and Research, funded by the New Zealand Ministry of Health.
* United States: Data provided publicly by the U.S. Centers for Disease Control.

Is there a way to export the data? How may the data be used?
Yes. The Download raw data page provides links to exported CSV files. Exported data may be used for any purpose, subject to the Google Terms of Service. If you choose to use the information, please make sure to appropriately attribute it to Google. If you're planning to publish using this data, please send a courtesy notification to flutrends-support@google.com. If possible, a representative will respond and answer additional questions you may have.

When are flu activity estimates revised?
Estimates for the current week are updated daily as new search query data is collected. However, once a week is over, the estimate for that week is final and not revised. Google Flu Trends weeks begin on Sunday and end on Saturday.
Understanding Flu Activity

What is an ILI percentage?
ILI stands for influenza-like illness. Public health agencies like the U.S Centers for Disease Control track the percentage of doctor visits each week which are related to ILI, gathering data from a network of sentinel healthcare providers. A high ILI percentage means that a large fraction of patients are experiencing influenza-like symptoms. These symptoms are often caused by seasonal influenza viruses, but other viruses can also cause influenza-like symptoms. A notable increase in ILI-related doctor visits may indicate a need for a public health inquiry to identify the pathogen or pathogens involved.

How do public health agencies use ILI percentages to monitor seasonal flu?
Traditional surveillance systems often rely on both virologic and clinical data. A network of sentinel laboratories may perform virologic testing by counting and classifying influenza viruses collected from patients, while a network of sentinel physicians will report the fraction of patients presenting with an influenza-like illness (ILI).

What is unique about Google's approach versus traditional collection mechanisms?
Google Flu Trends estimates flu activity for Australia, Mexico, New Zealand and the United States from aggregated search query data. The system provides users and health professionals with up-to-date estimates of flu activity in their region. Traditional surveillance reports come directly from doctors and other health service professionals, sometimes with a delay of up to 1-2 weeks.

When does flu season usually occur?
Flu is a seasonal disease in non-tropical countries, and flu season typically starts in late autumn. In the Northern hemisphere the flu season typically spans from November to March. In the Southern hemisphere the flu season typically spans from May to September. In tropical countries, a strong seasonal pattern may not exist.

How can I learn more about the flu?
To learn more about the flu, please consult the Ministry of Health, Centers for Disease Control, or flu surveillance network for your country.

What should I do if there are high levels of flu activity in my region?
According to U.S. CDC, the single best way to prevent seasonal flu is for individuals, especially people at high risk for serious complications from the flu, to get a vaccination. To learn more, see Key Facts about Flu Vaccine.

For information on H1N1, or swine flu please see the WHO site. Additional information can be found at the U.S. CDC site.
About Google.org

Is Google Flu Trends part of Google.org's work on preventing pandemics?
Google.org's Predict and Prevent initiative supports efforts to identify hotspots where new infectious diseases may emerge, detect new pathogens and outbreaks earlier, and respond quickly to prevent local threats from becoming global crises. The Google Flu Trends team worked closely with the Predict and Prevent team as the product was developed, and we continue to look for ways to use Google's tools and products to predict and prevent infectious disease outbreaks and other emerging threats. Read more about the Predict and Prevent initiative on the Google.org website.
Privacy and Terms of Use

When is it okay to use the information I find on Google Flu Trends?
You're free to use any of the information you find on Google Flu Trends, subject to the Google Terms of Service. If you choose to use the information, please make sure to appropriately attribute it to Google.

This tool makes search information public. What about my personal search data?
Your personal search data remains safe and private. Our graphs are based on aggregated data from millions of Google searches over time. Moreover, the results Google Flu Trends displays are produced by an automated system. See our Privacy Center for more about how we use search query data.

How is this related to Google Health? Is Flu Trends connected to my personal health records?
Google Flu Trends, like Google Health, supports Google's mission to organize the world's information and make it universally accessible and useful. Beyond that, there is no connection between the two products. We don't use personal health records or personally identifiable information to create our flu estimates. Only aggregated search queries are used to provide Google Flu Trends.

Can you tell more about what Google does with my personal search data?
Please read more at the Google Privacy FAQ.