Syndromic surveillance use to detect the early effects of heat-waves: An analysis of NHS direct data in England

Giovanni Leonardi, S. Hajat, R. S. Kovats, Gillian Smith, D. Cooper, E. Gerard

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Objectives: To investigate the effects of high ambient temperatures, including the summer 2003 heat-episode, on NHS Direct usage and its suitability as a surveillance tool in heat health warning systems. Methods: Analyses of data on calls to NHS Direct in English Regions in the period Dec 2001-May 2004. Outcomes were daily rates of all symptomatic calls, and daily proportion of calls for selected causes (fever, vomiting, diffi culty breathing, heat-/sun-stroke). Results: Total calls were moderately increased as environmental temperature increased; this effect was greatest in calls for young children and for fever. Total calls were moderately elevated during two summer heat episodes in 2003: calls specifically for heat/sun stroke increased acutely in response to these episodes. No association was apparent between environmental temperature and proportion of calls for vomiting and difficulty breathing. Conclusions: Calls to NHS Direct are sensitive to daily temperatures and extreme weather. NHS Direct is timely and has great potential in health surveillance. Calls for heat- and sun-stroke are now routinely monitored as part of the UK Heat-wave plan.

Original languageEnglish
Pages (from-to)194-201
Number of pages8
JournalSozial- und Praventivmedizin
Issue number4
Publication statusPublished - Nov 2006


  • Heat-waves
  • NHS Direct
  • Primary care
  • Surveillance
  • Temperature


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