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ISDS 2012 Conference Abstracts

Syndromic Surveillance Based on Emergency Visits: A
Reactive Tool for Unusual Events Detection
Pascal Vilain*1, Arnaud Bourdé2, Pierre-Jean Marianne dit Cassou3, Yves Jacques-
Antoine4, Philippe Morbidelli5 and Laurent Filleul1

1Regional Office of the French Institute for Public Health Surveillance of Indian Ocean, Saint-Denis, Reunion; 2University hospital,
Saint-Denis, Reunion; 3University hospital, Saint-Pierre, Reunion; 4Hopital center, Saint-Benoît, Reunion; 5Hopital center, Saint-Paul,
Reunion

Objective
To show with examples that syndromic surveillance system can be

a reactive tool for public health surveillance.

Introduction
The late health events such as the heat wave of 2003 showed the

need to make public health surveillance evolve in France. Thus, the
French Institute for Public Health Surveillance has developed syn-
dromic surveillance systems based on several information sources such
as emergency departments (1). In Reunion Island, the chikungunya out-
break of 2005-2006, then the influenza pandemic of 2009 contributed
to the implementation and the development of this surveillance system
(2-3). In the past years, this tool allowed to follow and measure the im-
pact of seasonal epidemics. Nevertheless, its usefulness for the detec-
tion of minor unusual events had yet to be demonstrated.

Methods
In Reunion Island, the syndromic surveillance system is based on

the activity of six emergency departments. Two types of indicators
are constructed from collected data:

- Qualitative indicators for the alert (every visit whose diagnostic
relates to a notifiable disease or potential epidemic disease);

- Quantitative indicators for the epidemic/cluster detection (num-
ber of visits based on syndromic grouping).

Daily and weekly analyses are carried out. A decision algorithm
allows to validate the signal and to organize an epidemiological in-
vestigation if necessary.

Results
Each year, about 150 000 visits are registered in the six emergency

departments that is 415 consultations per day on average. Several un-
usual health events on small-scale were detected early.

In August 2011, the surveillance system allowed to detect the first
autochthonous cases of measles, a few days before this notifiable disease
was reported to health authorities (Figure 1). In January 2012, the data
of emergency departments allowed to validate the signal of viral menin-
gitis as well as to detect a cluster in the West of the island and to follow
its trend. In June 2012, a family foodborne illness was detected from a
spatio-temporal cluster for abdominal pain by the surveillance system
and was confirmed by epidemiological investigation (Figure 2).

Conclusions
Despite the improvement of exchanges with health practitioners

and the development of specific surveillance systems, health sur-
veillance remains fragile for the detection of clusters or unusual
health events on small scale. The syndromic surveillance system
based on emergency visits has proved to be relevant for the identifi-
cation of signals leading to health alerts and requiring immediate con-
trol measures. In the future, it will be necessary to develop these
systems (private practitioners, sentinel schools) in order to have sev-
eral indicators depending on the degree of severity.

Figure 1. Epidemic curve of measles cases

Figure 2. Line-list of patient characteristics in an abdominal pain cluster.

Keywords
Syndromic surveillance; Unusual event detection; Reunion Island

Acknowledgments

We are thankful to all the practitioners of emergency departments.

References

1. Josseran L, Nicolau J, Caillère N, Astagneau P, Brücker G. Syndromic
surveillance based on emergency department activity and crude mor-
tality: two examples. Euro Surveill. 2006;11(12):225-9.

2. D’Ortenzio E, Do C, Renault P, Weber F, Filleul L. Enhanced in-
fluenza surveillance on Réunion Island (southern hemisphere) in the
context of the emergence of influenza A(H1N1)v. Euro Surveill.
2009;14(26). pii: 19257.

3. Filleul L, Durquety E, Baroux N, Chollet P, Cadivel A, Lernout T.
The development of non-specific surveillance in Mayotte and Re-
union Island in the contexte of the epidemic influenza A(H1N1) 2009
[Article in French]. Bull EpidemiolHebd. 2010:283.

*Pascal Vilain
E-mail: pascal.vilain@ars.sante.fr

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e150, 2013