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Detecting influenza epidemics using search engine query data

Nature volume 457, pages 10121014 (19 February 2009) | Download Citation


This article has been updated


Seasonal influenza epidemics are a major public health concern, causing tens of millions of respiratory illnesses and 250,000 to 500,000 deaths worldwide each year1. In addition to seasonal influenza, a new strain of influenza virus against which no previous immunity exists and that demonstrates human-to-human transmission could result in a pandemic with millions of fatalities2. Early detection of disease activity, when followed by a rapid response, can reduce the impact of both seasonal and pandemic influenza3,4. One way to improve early detection is to monitor health-seeking behaviour in the form of queries to online search engines, which are submitted by millions of users around the world each day. Here we present a method of analysing large numbers of Google search queries to track influenza-like illness in a population. Because the relative frequency of certain queries is highly correlated with the percentage of physician visits in which a patient presents with influenza-like symptoms, we can accurately estimate the current level of weekly influenza activity in each region of the United States, with a reporting lag of about one day. This approach may make it possible to use search queries to detect influenza epidemics in areas with a large population of web search users.

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Change history

  • 19 February 2009

    The AOP version of this paper published on 19 November 2008 contained an inaccuracy in the reference list.


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We thank L. Finelli for providing background knowledge, helping us validate results and comments on this manuscript. We are grateful to R. Rolfs, L. Wyman and M. Patton for providing ILI data. We thank V. Sahai for his contributions to data collection and processing, and C. Nevill-Manning, A. Roetter and K. Sarvian for their comments on this manuscript.

Author Contributions J.G. and M.H.M. conceived, designed and implemented the system. J.G., M.H.M. and R.S.P. analysed the results and wrote the paper. L.B. contributed data. All authors edited and commented on the paper.

Author information


  1. Google Inc., 1600 Amphitheatre Parkway, Mountain View, California 94043, USA

    • Jeremy Ginsberg
    • , Matthew H. Mohebbi
    • , Rajan S. Patel
    • , Mark S. Smolinski
    •  & Larry Brilliant
  2. Centers for Disease Control and Prevention, 1600 Clifton Road, NE, Atlanta, Georgia 30333, USA

    • Lynnette Brammer


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Corresponding author

Correspondence to Matthew H. Mohebbi.

Supplementary information

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    Supplementary Information 1

    This file contains Supplementary Figures 1-3 and Legends, Supplementary Methods and Supplementary Notes.

Excel files

  1. 1.

    Supplementary Information 2

    Query fractions for the top 100 search queries, sorted by mean Z-transformed correlation with CDC-provided ILI percentages across the nine regions of the United States.

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