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ISDS Annual Conference Proceedings 2012. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution, and
reproduction in any medium, provided the original work is properly cited.

ISDS 2012 Conference Abstracts

Increasing Mild Enterovirus Cases Provides An
Important Signal of Up-coming Trends in Elevating
Severe Enterovirus Cases
Ta-Chien Chan*1, Rung-Hung Chen2 and Chwan-Chuen King3

1Center for GIS, Research Center for Humanities and Social Sciences, Academia Sinica, Taipei City, Taiwan; 2Department of
Medicine, College of Medicine, National Taiwan University, Taipei City, Taiwan; 3Institute of Epidemiology and Preventive Medicine,
College of Public Health, National Taiwan University, Taipei City, Taiwan

Objective
This study was to elucidate the spatio-temporal correlations be-

tween the mild and severe enterovirus cases through integrating en-
terovirus-related three surveillance systems in Taiwan. With these
fully understanding epidemiological characteristics, hopefully, we
can develop better measures and indicators from mild cases to pro-
vide early warning signals and thus minimizing subsequent numbers
of severe cases.

Introduction
In July 2012, the 54 children infected with enterovirus-71(EV-

71) were died in Cambodia [1]. The media called it as mystery illness
and made Asian parents worried. In fact, the severe epidemics of en-
terovirus occurred frequently in Asia, including Malaysia, Singapore,
Taiwan and China [2]. The clinical severity varied from asympto-
matic to mild (hand-foot-mouth disease and herpangina) and severe
pulmonary edema/hemorrhage and encephalitis [3]. Up to now, the
development of vaccine for EV-71 and the more effective antiviral
drug was still ongoing [4]. Therefore, surveillance for monitoring the
enterovirus activity and understanding the epidemiological charac-
teristics between mild and severe enterovirus cases was crucial.

Methods
Three main databases including national notifiable diseases sur-

veillance, sentinel physician surveillance and laboratory surveillance
from July 1, 1999 to December 31, 2008 were analyzed. The Pear-
son’s correlation coefficient was applied for measuring the consis-
tency of the trend. The Poisson space-time scan statistic [5] was used
for identifying the most likely clusters. We used GIS (ArcMap, ver-
sion9.0; ESRI Inc.,Redlands, CA, USA) for visualization of detected
clusters.

Results
Temporal analysis found that the Pearson’s correlation between

mild EV cases and severe EV cases occurring in the same week was
0.553 (p<0.01) in Figure 1. Such a correlation became moderate
(data) when mild EV cases happened in 1~4 weeks before the current
severe EV cases. Among the 1,517 severe EV cases notified to Tai-
wan CDC during the study period, the mean age was 27 months,
61.4% was male and 12% were fatal. These severe EV cases were
significantly associated with the positive isolation rate of EV-71, with
much higher correlation than the mild cases [ 0.498 p<0.01 vs. 0.278,
p<0.01] . Using the space-time cluster method, we identified three
possible clusters in June 2008 in six cities/counties (Figure 2).

Conclusions
Taiwan’s surveillance data indicate that local public health pro-

fessionals can monitor the trends in the numbers of mild EV cases in
community to provide early warning signals for local residents to pre-
vent the severity of future waves.

Figure 1. The temporal trend between mild and severe EV cases.

Figure 2. The spatio-temporal clusters of EV severe cases.

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e108, 2013



ISDS Annual Conference Proceedings 2012. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution, and
reproduction in any medium, provided the original work is properly cited.

ISDS 2012 Conference Abstracts

Keywords
Enterovirus; Suveillance; Space Time Clusters

References

1. WHO, Severe complications of hand, foot and mouth disease
(HFMD) caused by EV-71 in Cambodia – conclusion of the joint in-
vestigation[http://www.who.int/csr/don/2012_07_13/en/index.html]

2. Lee MS, Chiang PS, Luo ST, Huang ML, Liou GY, Tsao KC, Lin TY:
Incidence rates of enterovirus 71 infections in young children during
a nationwide epidemic in Taiwan, 2008-09. PLoS Negl Trop Dis 2012,
6(2):e1476.

3. Chen SC, Chang HL, Yan TR, Cheng YT, Chen KT: An eight-year
study of epidemiologic features of enterovirus 71 infection in Taiwan.
Am J Trop Med Hyg 2007, 77(1):188-191.

4. Chang LY: Enterovirus 71 in Taiwan. Pediatr Neonatol 2008,
49(4):103-112.

5. Kulldorff M, Athas WF, Feurer EJ, Miller BA, Key CR: Evaluating
cluster alarms: a space-time scan statistic and brain cancer in Los
Alamos, New Mexico. Am J Public Health 1998, 88(9):1377-1380.

*Ta-Chien Chan
E-mail: dachianpig@gmail.com

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e108, 2013