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Public Health Surveillance for World Youth Day --- Toronto, Canada, 2002

Kate L. Bassil,1 B. Henry,2 E. Rea,1 M. Varia,3 D. Cole1
University of Toronto, Toronto, Canada; 2Toronto Public Health, Toronto, Canada; 3Health Canada, Ottawa, Ontario, Canada

Corresponding author: Kate L. Bassil, New College, 45 Willcocks Street, Toronto, Canada, ON M5S 1C7. Telephone: 416-946-0353; Fax: 416971-3072; E-mail:

Disclosure of relationship: The contributors of this report have disclosed that they have no financial interest, relationship, affiliation, or other association with any organization that might represent a conflict of interest. In addition, this report does not contain any discussion of unlabeled use of commercial products or products for investigational use.


Introduction: World Youth Day (WYD) is a biannual international Catholic event for persons aged 17--35 years. During July 13--28, 2002, WYD activities took place in Toronto, Canada; 176,100 persons registered to participate, and 800,000 persons attended an overnight vigil and papal mass. Because of the potential for imported communicable disease and local disease outbreaks, Toronto Public Health, Health Canada, and WYD organizers developed a surveillance network to facilitate timely public health response.

Objectives: This study assessed the effectiveness of the syndromic surveillance network established for WYD 2002.

Methods: The surveillance network collected data from multiple sources, including 1) all WYD medical facilities, 2) emergency departments (EDs), 3) pharmacies, and 4) 9-1-1 emergency calls. Surveillance activities were coordinated from a downtown Toronto office staffed by physicians, epidemiologists, community medicine residents, and administrators. Findings were communicated daily to public health and WYD authorities. Ten syndrome definitions were developed on the basis of outbreak potential, public interest, and need for timely detection. Cumulative mean count, two standard deviations from the rolling 7-day mean, and CUMSUM methods were used for the analysis.

Results: Although no substantial outbreaks occurred, enough activity was noted to indicate that an event would have been detected if it had occurred. Activity included a case of malaria, a case of chickenpox, and an outbreak of foodborne illness involving 18 persons. In addition, 3,332 (21%) of 15,717 ED visits, 4,394 (39%) of 11,250 calls to 9-1-1, and approximately 35% of onsite clinic visits met syndrome definitions. Heatrelated illness was the most prevalent event documented, with an increased proportion of 9-1-1 calls and the most common syndrome (n = 105) above two standard deviations from the rolling mean reported through EDs. Heat-related illness also was the most frequent onsite clinic diagnosis received by WYD participants among >5,000 visits during 6 days.

Conclusion: For an event-specific syndromic surveillance network to be effective, multiple data sources and redundancy are needed. A range of communication channels, back-up methods for data collection, and complementary surveillance components were employed for this event. Substantial time, resources, and planning were required for the implementation of this surveillance network. However, certain activities that are feasible for event-specific surveillance are difficult to sustain on an ongoing basis because of a lack of resources. For this reason, monitoring 9-1-1 calls appears to offer the greatest potential usefulness for ongoing public health surveillance.

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Date last reviewed: 8/5/2005


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