Epidemiology and Infection

  • Epidemiology and Infection / Volume 142 / Issue 02 / February 2014, pp 303-313
  • Copyright © Cambridge University Press 2013 The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution-NonCommercial-ShareAlike licence <http://creativecommons.org/licenses/by-nc-sa/3.0/>. The written permission of Cambridge University Press must be obtained for commercial re-use.
  • DOI: http://dx.doi.org/10.1017/S0950268813001088 (About DOI), Published online: 15 May 2013

Original Papers

Gastroenteritis and outbreaks

Syndromic surveillance for local outbreak detection and awareness: evaluating outbreak signals of acute gastroenteritis in telephone triage, web-based queries and over-the-counter pharmacy sales


a1 Swedish Institute for Communicable Disease Control (SMI), Solna, Sweden

a2 National Food Agency (SLV), Sweden

a3 Division for Mathematical Statistics, Department of Mathematics, Stockholm University, Sweden

a4 Inera AB, Sweden

a5 Department of Microbiology, Tumour and Cell Biology, Karolinska Institutet, Sweden

a6 County Medical Officer, Västerbotten, Sweden

a7 Department of Clinical Microbiology, Umeå University, Sweden


For the purpose of developing a national system for outbreak surveillance, local outbreak signals were compared in three sources of syndromic data – telephone triage of acute gastroenteritis, web queries about symptoms of gastrointestinal illness, and over-the-counter (OTC) pharmacy sales of antidiarrhoeal medication. The data sources were compared against nine known waterborne and foodborne outbreaks in Sweden in 2007–2011. Outbreak signals were identified for the four largest outbreaks in the telephone triage data and the two largest outbreaks in the data on OTC sales of antidiarrhoeal medication. No signals could be identified in the data on web queries. The signal magnitude for the fourth largest outbreak indicated a tenfold larger outbreak than officially reported, supporting the use of telephone triage data for situational awareness. For the two largest outbreaks, telephone triage data on adult diarrhoea provided outbreak signals at an early stage, weeks and months in advance, respectively, potentially serving the purpose of early event detection. In conclusion, telephone triage data provided the most promising source for surveillance of point-source outbreaks.

(Received September 25 2012)

(Revised March 27 2013)

(Accepted April 17 2013)

(Online publication May 15 2013)

Key words

  • Foodborne infections;
  • outbreaks;
  • statistics;
  • syndromic surveillance;
  • waterborne infections


c1 Author for correspondence: Dr T. Andersson, Swedish Institute for Communicable Disease Control (SMI), 171 82 Solna, Sweden. (Email: tom.andersson@msb.se)