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. 2017 Apr 18;17(1):328.
doi: 10.1186/s12889-017-4233-8.

Early outbreak detection by linking health advice line calls to water distribution areas retrospectively demonstrated in a large waterborne outbreak of cryptosporidiosis in Sweden

Pär Bjelkmar  1 , Anette Hansen  2 , Caroline Schönning  3 , Jakob Bergström  3 , Margareta Löfdahl  3 , Marianne Lebbad  2 , Anders Wallensten  3   4 , Görel Allestam  3 , Stephan Stenmark  5 , Johan Lindh  6
Affiliations

Early outbreak detection by linking health advice line calls to water distribution areas retrospectively demonstrated in a large waterborne outbreak of cryptosporidiosis in Sweden

Pär Bjelkmar et al. BMC Public Health. .

Abstract

Background: In the winter and spring of 2011 a large outbreak of cryptosporidiosis occurred in Skellefteå municipality, Sweden. This study summarizes the outbreak investigation in terms of outbreak size, duration, clinical characteristics, possible source(s) and the potential for earlier detection using calls to a health advice line.

Methods: The investigation included two epidemiological questionnaires and microbial analysis of samples from patients, water and other environmental sources. In addition, a retrospective study based on phone calls to a health advice line was performed by comparing patterns of phone calls between different water distribution areas.

Results: Our analyses showed that approximately 18,500 individuals were affected by a waterborne outbreak of cryptosporidiosis in Skellefteå in 2011. This makes it the second largest outbreak of cryptosporidiosis in Europe to date. Cryptosporidium hominis oocysts of subtype IbA10G2 were found in patient and sewage samples, but not in raw water or in drinking water, and the initial contamination source could not be determined. The outbreak went unnoticed to authorities for several months. The analysis of the calls to the health advice line provides strong indications early in the outbreak that it was linked to a particular water treatment plant.

Conclusions: We conclude that an earlier detection of the outbreak by linking calls to a health advice line to water distribution areas could have limited the outbreak substantially.

Keywords: Cryptosporidiosis; Cryptosporidium hominis; Early outbreak detection; Syndromic surveillance.

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Figures

Fig. 1
Fig. 1
Time line indicating for which time periods the different data sources were used in the analyses
Fig. 2
Fig. 2
Epidemiological curve based on observed cases in the web questionnaire
Fig. 3
Fig. 3
Epidemiological curve of population estimates of number of cases from the postal questionnaire
Fig. 4
Fig. 4
Daily call counts from Skellefteå municipality to Healthcare Guide 1177 regarding GI symptoms from 1 August 2010 until the day before the BWN on 19 April 2011. Inhabitants are divided into two groups; those living in the water distribution area of Abborrverket WPT (blue) and those who are not (red). Outbreak signals from the detection algorithm [14] are shown as blue (Abborrverket WTP) and red circles (not Abborrverket WTP) with weak (hollow circles) and strong outbreak signals (filled circles) along the lower horizontal and upper horizontal, respectively
See this image and copyright information in PMC

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