Frequently asked questions

About Google Flu Trends

What information is provided by Google Flu Trends?
Google Flu Trends provides near real-time estimates of flu activity for a number of countries and regions around the world based on aggregated search queries. Some of these estimates have been validated through comparison with official historic influenza data from the relevant country or region. Generally, countries labeled as "experimental" have not been formally compared against official influenza data. Both validated and unvalidated estimates can be viewed on the Google Flu Trends website or downloaded as a CSV file for analysis. Read more about how Google Flu Trends works.

How are the flu activity levels determined?
Google Flu Trends compares the estimates based on search data against a historic baseline level of flu activity for that area. Depending on whether the current estimate is higher or lower than the baseline, Google 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.

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, however it is possible that future estimates may deviate from actual flu activity.

How is Google Flu Trends useful for pandemic flu?
Google Flu Trends models are validated using historic flu surveillance data. When a new flu virus causes the same symptoms as seasonal flu, Google Flu Trends should detect if overall flu rates are significantly increasing.

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?
We currently have estimates for more than 25 countries. Anyone connected to the Internet can access Google Flu Trends.

What organizations provided flu data for each country or region?

Is there a way to export the data?
Yes. The "Data" link on each country page provides the option to download the data.

How should the exported data be interpreted?
In most cases, raw numbers in each data file can be interpreted as the estimated number of ILI cases per 100,000 population; however, in Bulgaria, Germany, Ukraine, and South Africa the numbers represent ARI cases per 100,000 population. Australia, Canada, Chile and US flu activity levels are estimated as ILI cases per 100,000 physician visits. Romania flu activity levels are estimated as combined ILI and ARI per 100,000 physician visits.

Is there a way to embed the charts on my own website?
Yes, from each country page click the "embed chart" link to access the code snippet that will enable you to embed that country's chart widget on your website.

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.

Will Google Flu Trends and Google Dengue Trends someday include other diseases?
The team found the methodology works for flu and for dengue, but there are no plans to add additional diseases at this time.

How can I send feedback about Google Flu Trends?
Please share your feedback using this form.

Understanding Flu Activity

What are ILI, ARI and virilogic data?
ILI, ARI and virilogic data provide different ways of measuring the level of influenza in a population. ILI stands for influenza-like illness. Public health agencies often 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 flu-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.

ARI stands for acute respiratory infection. Influenza is one cause of ARI, and thus public health agencies often track the percentage of doctor visits each week which are related to ARI, similar to ILI, gathering data from a network of sentinel healthcare providers.

Virilogic data reflects laboratory confirmed cases of influenza. A percentage will be provided based on the number of positive laboratory confirmed cases over the total number of samples tested.

How do public health agencies use influenza data 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) or acute respiratory infection (ARI).

What is unique about Google's approach versus traditional collection mechanisms?
Google Flu Trends estimates flu activity for a number of countries by using aggregated search query data. The system provides users and public health officials with near real-time 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 or region.

What should I do if there are high levels of flu activity in my region?
Please consult the Ministry of Health or Centers for Disease Control in your country or region for official guidance regarding flu.


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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 attribute it to Google as follows: "Data Source: Google Flu Trends (".

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.

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