Google search patterns monitoring the daily health impact of heatwaves in England: How do the findings compare to established syndromic surveillance systems from 2013 to 2017?

Helen Green, Obaghe Edeghere, Alex Elliot, Ingemar J. Cox, Roger Morbey, Richard Pebody, Angie Bone, Rachel A. McKendry, Gillian Smith*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


One of the implications of climate change is a predicted increase in frequent and severe heatwaves. The impact of heatwaves on the health of the population is captured through real-time syndromic healthcare surveillance systems monitored daily in England during the summer months. Internet search data could potentially provide improved timeliness and help to assess the wider population health impact of heat by capturing a population sub-group who are symptomatic but do not seek healthcare. A retrospective observational study was carried out from June 2013 to September 2017 in England to compare daily trends in validated syndromic surveillance heat-related morbidity indicators against symptom-based heatwave related Google search terms. The degree of correlation was determined with Spearman correlation coefficients and lag assessment was carried out to determine timeliness. Daily increases in frequency in Google search terms during heatwave events correlated well with validated syndromic indicators. Correlation coefficients between search term frequency and syndromic indicators from 2013 to 2017 were highest with the telehealth service NHS 111 (range of 0.684–0.900 by search term). Lag analysis revealed a similar timeliness between the data sources, suggesting Google data did not provide a delayed or earlier signal in the context of England's syndromic surveillance systems. This work highlights the potential benefits for countries which lack established public health surveillance systems to monitor heat-related morbidity and the use of internet search data to assess the wider population health impact of exposure to heat.

Original languageEnglish
Pages (from-to)707-712
Number of pages6
JournalEnvironmental Research
Publication statusPublished - Oct 2018

Bibliographical note

Funding Information:
We acknowledge support from: NHS 111 and NHS Digital for their assistance and support with the NHS 111 system; OOH providers submitting data to the GPOOHSS and Advanced Heath & Care; ED clinicians and NHS Trust staff supporting EDSSS, the Royal College of Emergency Medicine and technical support provided by EMIS Health and L2S2 Ltd; TPP and participating SystmOne practices and University of Nottingham, ClinRisk, EMIS and EMIS practices submitting data to the QSurveillance database and Google for access to their Google Health Trends API. The authors would like to thank Mr Paul Loveridge of the PHE Real-time Syndromic Surveillance Team (ReSST) and Dr Bill Lampos of the Department of Computer Science, UCL for their technical expertise. IJC and RAM are supported by the i-sense EPSRC IRC in Early Warning Sensing Systems for Infectious Diseases (EP/K031953/1) and RAM is also supported by the Royal Society Wolfson Merit Award. AJE and GES are supported by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Emergency Preparedness and Response at King's College London in partnership with PHE. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or Public Health England.

Publisher Copyright:
© 2018


  • Heat-related illness
  • Heat-waves
  • Public health
  • Syndromic surveillance
  • Temperature


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