Cited by 381Data-Driven Disease SurveillanceInfluenza Virus Research StudiesRespiratory viral infections research

Assessing Google Flu Trends Performance in the United States during the 2009 Influenza Virus A (H1N1) Pandemic

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Cook, Samantha, Conrad, Corrie, Fowlkes, Ashley L., Mohebbi, Matthew H.·2011·PLoS ONE

Abstract

BACKGROUND: Google Flu Trends (GFT) uses anonymized, aggregated internet search activity to provide near-real time estimates of influenza activity. GFT estimates have shown a strong correlation with official influenza surveillance data. The 2009 influenza virus A (H1N1) pandemic [pH1N1] provided the first opportunity to evaluate GFT during a non-seasonal influenza outbreak. In September 2009, an updated United States GFT model was developed using data from the beginning of pH1N1. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the accuracy of each U.S. GFT model by comparing weekly estimates of ILI (influenza-like illness) activity with the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet). For each GFT model we calculated the correlation and RMSE (root mean square error) between model estimates and ILINet for four time periods: pre-H1N1, Summer H1N1, Winter H1N1, and H1N1 overall (Mar 2009-Dec 2009). We also compared the number of queries, query volume, and types of queries (e.g., influenza symptoms, influenza complications) in each model. Both models' estimates were highly correlated with ILINet pre-H1N1 and over the entire surveillance period, although the original model underestimated the magnitude of ILI activity during pH1N1. The updated model was more correlated with ILINet than the original model during Summer H1N1 (r = 0.95 and 0.29, respectively). The updated model included more search query terms than the original model, with more queries directly related to influenza infection, whereas the original model contained more queries related to influenza complications. CONCLUSIONS: Internet search behavior changed during pH1N1, particularly in the categories "influenza complications" and "term for influenza." The complications associated with pH1N1, the fact that pH1N1 began in the summer rather than winter, and changes in health-seeking behavior each may have played a part. Both GFT models performed well prior to and during pH1N1, although the updated model performed better during pH1N1, especially during the summer months.

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  • The ad hoc method of throwing out peculiar search terms failed when GFT completely missed the nonseasonal 2009 influenza A-H1N1 pandemic.

    “This ad hoc method of throwing out peculiar search terms failed when GFT completely missed the nonseasonal 2009 infl uenza A–H1N1 pandemic ( 2, 14).”

    From The Parable of Google Flu: Traps in Big Data Analysis (2014) · cites this paper as [14]

    The Abstract (Methodology/Principal Findings) says the original GFT model underestimated the magnitude of illness during the 2009 H1N1 pandemic, not that it completely missed it. The Abstract (Conclusions) says both models performed well during the pandemic, although the updated model performed better. The Discussion notes that pandemic-specific queries were excluded, but does not describe this as an ad hoc method of throwing out peculiar terms. (LLM, conf=0.88)

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  • The few search terms offered in the GFT papers do not seem to be strongly related with either GFT or the CDC data.

    “Oddly, the few search terms offered in the papers ( 14) do not seem to be strongly related with either GFT or the CDC data (SM)—we surmise that the authors felt an unarticulated need to cloak the actual search terms identifi ed.”

    From The Parable of Google Flu: Traps in Big Data Analysis (2014) · cites this paper as [14]

    The Results section (‘Search Behavior During pH1N1’; page unavailable) says that all three search queries shown in Figure 3 closely tracked CDC ILINet data before the pandemic, and ‘symptoms of flu’ continued to do so during it. The paper does report that the bronchitis and pneumonia queries underestimated ILINet data during the pandemic, but that does not support the broad claim that the offered terms were not strongly related to the data. (LLM, conf=0.87)

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  • GFT has never documented the 45 search terms used, and the examples that have been released appear misleading.

    “GFT has never documented the 45 search terms used, and the examples that have been released appear misleading ( 14) (SM).”

    From The Parable of Google Flu: Traps in Big Data Analysis (2014) · cites this paper as [14]

    The Results (Model Composition) show that only 14% of original-model queries contained “flu” and that complication-related queries accounted for 48% of its query volume, supporting concern that flu-focused examples could misrepresent the model. But the paper does not say that GFT never documented its search terms or identify previously released examples as misleading; it describes the original model as having approximately 40 queries, not 45. (LLM, conf=0.72)

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Research works printed but not linked: 1

  1. [5]Wilson N Mason K Tobias M Peacey M Huang QS 2009 Interpreting “GFT” Data for Pandemic H1N1: The New Zealand Experience. EuroSurveill 14 44 pii = 19386 Available: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19386. Accessed 2011 July 28 19941777

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Authors
Cook, S., Conrad, C., Fowlkes, A. L., & Mohebbi, M. H.
Affiliations
  • Google (United States) (US)
  • Google (United Kingdom) (GB)
  • Centers for Disease Control and Prevention (US)
Corresponding author
Conrad, Corrie
Venue
PLoS ONE
Published
2011-08-19
Volume
6
Issue
8
Pages
e23610
ISSN
1932-6203 (ISSN-L)
OpenAlex
W1998956117
Cited by
381
References
10
Citations by year
2026: 5 · 2025: 4 · 2024: 7 · 2023: 8 · 2022: 25 · 2021: 33 · 2020: 50 · 2019: 25 · 2018: 26 · 2017: 34 · 2016: 41 · 2015: 48 · 2014: 38 · 2013: 27 · 2012: 9
FWCI
18.08
Type
journal article
Language
en
Open access
Locations
  • PLoS ONE (publishedVersion, public-domain)
  • Europe PMC (PubMed Central) (publishedVersion, public-domain)
  • PubMed Central (publishedVersion, public-domain)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Google
Topics
  • Health Sciences › Medicine › Epidemiology › Data-Driven Disease Surveillance
  • Health Sciences › Medicine › Epidemiology › Influenza Virus Research Studies
  • Health Sciences › Medicine › Epidemiology › Respiratory viral infections research
Keywords
Google Flu Trends, influenza surveillance, 2009 H1N1 pandemic, influenza-like illness, online search behavior, health-seeking behavior, model accuracy assessment
MeSH terms
Humans, Influenza, Human, Models, Biological, Population Surveillance, Time Factors, United States, Influenza A Virus, H1N1 Subtype, Search Engine, Pandemics

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