An enhanced surveillance system for large events


Volume 45-7/8, July 4, 2019: Zoonotic diseases

Implementation science

A public health enhanced surveillance system for a mass gathering event

C Huot1, A Paradis2, K Hammond-Collins3, MA Bélair4, J Villeneuve5, N Brousseau1, I Goupil-Sormany1,2, J Riffon1


1 Direction de santé publique du Centre intégré universitaire de santé et de services sociaux de la Capitale-Nationale, Québec, QC

2 Département de médecine sociale et préventive, Université Laval, Québec, QC

3 Centre for Food-borne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Ottawa, ON

4 Centre for Emergency Preparedness and Response, Public Health Agency of Canada, Whitehorse, YK

5 Institut national de santé publique du Québec, Québec, QC


Suggested citation

Huot C, Paradis A, Hammond-Collins K, Bélair MA, Villeneuve J, Brousseau N, Goupil-Sormany I, Riffon J. A public health enhanced surveillance system for a mass gathering event. Can Commun Dis Rep 2019;45(7/8):212–24.

Keywords: mass gathering event, surveillance, syndromic surveillance, public health, epidemiology


Background: From June 7 to June 9, 2018, a G7 Summit was held in the Canadian province of Quebec. This international political mass gathering event posed a number of potential risks to public health.

Objective: To assess three additional monitoring strategies to detect public health threats during a mass gathering event.

Intervention: In addition to routine public health monitoring, a partnership was created and three monitoring strategies were put in place three days before, during and six days after the G7 event: the analysis of data on the presenting complaint and discharge diagnosis from 11 emergency departments in the area using the logiciel Early Aberration Reporting System; the daily polling of key health partners with an online questionnaire; and the analysis of calls to Info-Santé, a government-run telephone consultation service for the public regarding health and social issues.

Results: Emergency room data produced 78 alerts from the presenting complaints and 39 alerts from the discharge diagnoses. Of these 117 alerts, two were investigated (one in the respiratory and one in the neurological-muscular categories) and no other interventions were required. With a few exceptions, all of the health partners completed the online survey each day and no signal of concern was generated. Compared with historical data, no increase or differences in calls to Info-Santé were detected during the monitoring period.

Conclusion: The three additional monitoring strategies developed to detect events of public health importance during the 2018 G7 Summit in Quebec were successful in gathering timely data for analysis. Close collaboration and good participation from the different partners were essential to this project. However, because no public health event occurred, it was not possible to determine whether the enhanced surveillance system had sufficient speed and sensitivity for timely detection and response.


From June 7 to June 9, 2018, the prime minister of Canada hosted a G7 Summit in La Malbaie and Québec, QuebecFootnote 1. Seven internationally protected persons and their delegations (approximately 3,200 people), 3,200 journalists, thousands of demonstrators, 1,000 to 2,000 police officers, 1,000 service members from the Canadian Armed Forces and approximately 12,000 people from a number of non-G7 countries invited as part of the Outreach Program were expected to attend.

In preparation for this event, experts in emergency management were consulted, and the literatureFootnote 2Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7Footnote 8Footnote 9, including lessons learned from the Summit of the Americas in 2001Footnote 10, was reviewed. A number of monitoring initiatives previously applied during sportingFootnote 3Footnote 11Footnote 12Footnote 13Footnote 14Footnote 15Footnote 16Footnote 17Footnote 18Footnote 19, religiousFootnote 5Footnote 20Footnote 21 and artistic eventsFootnote 22Footnote 23 have been described previously. However, there was less detailed information available about surveillance during political events, especially those that are at risk for violent demonstrations or acts of terrorismFootnote 24Footnote 25.

In advance of the event, a number of potential public health threats were identified and prioritized for monitoring: rapid spread of certain infectious diseases; violence associated with demonstrations and use of crowd-control agents; potential for chemical, biological, radiological, nuclear or explosive (CBRNE) terrorist threats; and presence of suspicious packagesFootnote 26. Although the probability of these threats was considered lowFootnote 11Footnote 12Footnote 13Footnote 14Footnote 15Footnote 16Footnote 27, an enhanced surveillance system was needed to quickly detect potential public health threatsFootnote 28Footnote 29Footnote 30Footnote 31, as well as a rapid intervention plan for each of these threats.

Routine public health surveillance in Quebec relies on the mandatory reporting of notifiable diseases by physicians and laboratories, and on the passive reporting of perceived or real public health threats by various partners, including clinicians, government departments and local municipalitiesFootnote 32. However, these routine surveillance activities lacked the necessary sensitivity and timeliness to rapidly detect and respond to priority public health threats during the G7 SummitFootnote 33. To address this, the Direction de santé publique (DSPublique) of the Centre intégré universitaire de santé et de services sociaux de la Capitale-Nationale (Public Health Department of the National Capital Integrated University Health and Social Services Centre) developed an enhanced surveillance system that included activities for the period from June 4 to June 15, 2018 (three days before, three days during and six days after the event). The goal of the enhanced surveillance system was to develop a surveillance capacity that met the goals of early detection and acceptability to all participating partners.

The purpose of this article is to describe the development and outcome of three monitoring strategies that were part of the enhanced surveillance system during the 2018 G7 Summit, and to consider the implications of these strategies for public health surveillance during future mass gathering events.

Establishing partnerships

Approximately six months before the event, a DSPublique project team began the development of an enhanced surveillance system. All of the region’s emergency departments (ED) already had in place electronic records for both presenting complaints (those given by patients to the triage nurses when they came into the ED) and medical discharge diagnoses (those given by a physician when the patient left the ED). Not all these data are usually available to the DSPublique, and they had not been previously used for public health surveillance. The EDs of six university hospital centres and five regional hospital centres within the event perimeter or nearby were invited to collaborate for this event. To ensure access to these data, additional partners from other Integrated University Health and Social Services Centre departments collaborated with the DSPublique project team.

To receive daily reports from key partners, five organizations likely to detect the targeted threats early were approached: the Centre antipoison du Québec (Quebéc Poison Control Centre); the region's ambulance services; the Laboratoire de santé publique du Québec (Quebec Public Health Laboratory); and the Bureau du coroner (Quebec Coroner’s Office). Info-Santé (a public telephone consultation service for health and social issues) was a key partner that provided daily reports and contributed data for enhanced surveillance. Three temporary clinics were set up for the event and also submitted daily reports.

In addition to the partners who directly contributed to the enhanced surveillance system, the region’s clinicians were informed of the project’s progress stage-by-stage through the emergency management structure, which was put on alert for the event. The Public Health Agency of Canada provided support, deploying two field epidemiologists for planning, analyzing data and producing reports. All the enhanced monitoring activities were timed to allow for rapid analysis and dissemination of results, decision-making and response. A daily report summarizing the results was prepared and distributed to the DSPublique, partners and decision-makers. Two versions (short and detailed), adapted to the target audiences, were available.

Enhanced monitoring activities

To enhance the sensitivity and timeliness of the surveillance system, while ensuring it remained acceptable to all partners, the following three monitoring activities were added to Notifiable Disease reporting and passive reporting for the period from June 4 to June 15, 2018:

  • Monitoring trends in presenting complaints and discharge diagnoses at ED
  • Requesting daily reports from key partners
  • Monitoring trends in calls to Info-Santé

Monitoring trends from emergency departments

For the ED electronic data, presenting complaints were recorded by the triage nurse following a patients’ arrival, and medical discharge diagnoses were recorded when the patient was ready to leave the ED. All university hospital patients were identified with a unique identifier number. These data were available the day after the visit. Electronic record data from all ED visits in the area surrounding the G7 Summit were incorporated into the enhanced surveillance system. This approach was acceptable to clinical partners because these data were already available for other purposes. However, it did create a slight increase in workload, as reminders were sent if there were entry delays.

The discharge diagnoses were identified according to the International Classification of Diseases, 10th revision (ICD-10) as per the Quebec guidelinesFootnote 34. Selected presenting complaints and discharge diagnoses were sorted and analyzed by category (see Appendix 1 and Appendix 2). A few discharge diagnoses were also analyzed individually; these included either a notifiable disease or a diagnosis for which a public health response may be indicated for a single case, such as measles (see last column in Appendix 2). Two clinicians—one specializing in CBRNE emergencies and the other in clinical toxicology—validated the choices.

The number of cases in each category was analyzed using the Centers for Disease Control and Prevention's Early Aberration Reporting SystemFootnote 35 software, which detects alerts or aberrations in the number of cases based on short-term historical data (ten days). All the generated alerts were compared with historic data for the period of April to July 2013–2017. A daily analysis of the previous day’s data was conducted, by emergency department and for all emergency departments combined. Age group, municipality of the cases and details on the presenting complaints and diagnoses were used when available. A team evaluation and decision were made regarding whether or not to further investigate each alert that was generated.

Daily reports from key partners

Key partners included Quebéc’s Poison Control Centre, the region's ambulance services, the Quebec Public Health Laboratory, the Coroner’s Office, Info-Santé and three temporary clinics. A short, three-question online questionnaire (Voxco Inc. platform)Footnote 36 was developed and sent to respondents from partner organizations on a daily basis (before, during and after the event) regarding infectious or environmental health threats. Questionnaires were completed by 10 am regarding information from the previous day.

Monitoring trends for calls to Info-Santé

Electronic data on the reasons for calling Info-Santé were already available to the DSPublique, but had not previously been used for surveillance. The most relevant reasons for calling were selected based on the priority threats (Table 1). These reasons were sorted into categories for enhanced surveillance. In each category, the number and percentage of calls were analyzed on a daily basis to detect any increase or change compared with historical data.

Table 1: Monitored reasons for calling Info-Santé by category
Category Reasons for calling
Cardiovascular Cardiovascular system manifestations or symptoms
CBRNE/physical/environmental Extreme heat
Large events
Environmental health
Cutaneous/lymphatic Skin and tissue manifestations or symptoms
Extreme Avian influenza (bird flu)
Ebola virus
Gastrointestinal Gastrointestinal system manifestations or symptoms
Infectious Infectious and parasitic diseases
Neurological/muscular Nervous system manifestations or symptoms
Ophthalmological/ otorhinolaryngological Ophthalmic manifestations or symptoms
Respiratory Influenza-like illness
Respiratory problems excluding the flu


Emergency department data

During the monitoring period, data were available for both the presenting complaints and the discharge diagnoses. No presenting complaint data were missing. Overall, 27% of diagnosis data were missing during the entire monitoring period, which extended from June 4 to 15. During the G7 Summit (June 7 to 9), however, only 23% of diagnosis data were missing. These missing data were due to patients leaving the ED before a diagnosis was made and delays in the entry of diagnoses into the electronic record.

Emergency department data produced 78 alerts for the presenting complaint categories and generated 39 alerts in the various diagnosis categories. Among these 117 alerts, two were investigated (one for respiratory category and one for neurological-muscular category). No other intervention was required. Table 2 summarizes the number of alerts per category.

Table 2: Number of alerts by presenting complaint and discharge diagnosis category from 11 emergency departments in the La Malbaie/Québec region, June 4–15, 2018
Category Number of alerts
Presenting complaints Discharge diagnosis
Cardiovascular 5 3
CBRNE/physical/environmental 6 4
Cutaneous/lymphatic 6 4
Fever 9 n/a
Gastrointestinal 9 0
Hemorrhagic 8 6
Infectious n/a 5
Opioid intoxication n/a 0
Neurological/muscular 8 8
Ophthalmic/Otorhinolaryngological 9 4
Respiratory 5 2
Systemic/dehydration 13 3
TOTAL 78 39

Daily reports and Info-Santé

With a few exceptions, all of the partners completed the survey every day and few reminders were required. One of the three temporary clinics reported two cases of gastroenteritis. Ambulance services reported one case of opioid intoxication. Given that these reports did not exceed the expected frequency and there were no related health threats, none of these reports was investigated.

In analyzing the reasons for calls to Info-Santé, neither increases nor differences were detected during the monitoring period in comparison with historical data.


A three-pronged enhanced surveillance system, developed to detect events of public health importance during the 2018 G7 Summit in Quebec, was successful in gathering timely data for analysis. Most alerts were generated from the analysis of ED data. The use of historical data made it possible to limit the number of alerts for which an investigation was needed. The use of these data appeared to result in high sensitivity but low specificity.

A strength of this enhanced surveillance system was the close collaboration with a number of different partners. This collaboration was essential to the development of this enhanced surveillance system. The three additional monitoring strategies exhibited a high level of participation by the partners. This was likely because partners understood the importance of the additional monitoring and because only minimal additional time was required by participants. Thus, most data requested from the partners were received in a timely manner.

This work identified the feasibility of our enhanced surveillance system and could inform future public health preparedness for mass gathering events. However, because no public health event occurred, it was not possible to determine whether the enhanced surveillance system had sufficient speed and sensitivity for timely detection and response.


Three additional monitoring strategies developed to detect events of public health importance during the 2018 G7 Summit in Quebec were successful in gathering timely data for analysis. However, further assessment of speed and sensitivity is needed if applied to a future public health surveillance strategy of a mass gathering event.

Authors’ statement

  • HC — Conceptualization, methodology, intervention, analysis and interpretation of data, article writing
  • AP — Conceptualization, methodology, intervention, analysis and interpretation of data, article review
  • KHC — Intervention, analysis and interpretation of data, article review
  • MAB — Analysis and interpretation of data, article review
  • JV — Conceptualization, methodology, article review
  • NB — Intervention, analysis and interpretation of data, article review
  • IGS —Conceptualization, resources, article review
  • JR — Intervention, analysis and interpretation of data, article review

Conflict of interest



The authors would like to acknowledge the assistance of the following colleagues: FW Tremblay, M Mercier, F Desbiens, N Beaulieu, I Beaulieu, C Thibault, A Paradis, N Allain-Boulé, M Beauregard, A Maurice, N Thériault, J Lizotte, S Gaudreault, J Larocque, S Blais, D Martineau, V Tremblay, R Dion, È Pilon, and M St-Onge.


This work was supported by the Centre intégré universitaire de santé et de services sociaux de la Capitale-Nationale and the Public Health Agency of Canada.

Appendix 1: Monitored presenting complaints from emergency departments, by category

Category Presenting complaint
Cardiovascular Cardiac arrest (non-traumatic)
Chest pain—cardiac features
CBRNE/physical/environmental Noxious inhalation
Chemical exposure
Exposure to communicable disease
Cutaneous/lymphatic Reddened hot limb
Neck swelling/pain
Groin pain/mass
Localized swelling/redness
Other skin conditions
Lumps, bumps, calluses
Fever Fever
Gastrointestinal Diarrhea
Blood in stool/melena
Abdominal pain
Diarrhea and fever
Hemorrhagic Epistaxis
Vomiting blood
Spontaneous bruising
Neurological/muscular Difficulty swallowing/dysphagia
Altered level of consciousness
Gait disturbance/ataxia
Extremity weakness/symptoms of cerebrovascular accident
Ophthalmological/Otorhinolaryngological Sore throat
Chemical exposure, eye
Visual disturbance
Red eye, discharge
Eye pain
Eye trauma
Respiratory Symptoms of upper respiratory tract infection
Chest pain—non-cardiac features
Respiratory arrest
Wheezing—no other complaints
Cough and fever/Influenza-like illness
Systemic/dehydration General weakness

Appendix 2: Monitored discharge diagnoses with ICD-10 code from emergency departments, by categoryAppendix 2 table footnote a

Category ICD-10 code ICD-10 diagnosis Individual analysis done (Y/N)
Cardiovascular I20.0 Unstable angina N
I20.9 Angina pectoris N
I21.9 Acute myocardial infarction N
I24.9 Acute ischemic heart disease, acute coronary syndrome (ACS) N
I46.9 Cardiac arrest N
I95.9 Hypotension N
R00.1 Bradycardia N
R07.2 Chest pain of unknown cause N
R07.3 Anterior chest-wall pain N
R07.4 Chest pain N
R57.0 Cardiogenic shock N
CBRNE/physical/environmental J68.9 Inhalation of toxic products Y
T59.9 Toxic effect: gases, fumes and vapours Y
T62.9 Noxious substance eaten as food Y
T67.0 Heatstroke and sunstroke Y
T52.9 Toxic effect: organic solvent N
T54.9 Toxic effect: corrosive substance N
T58 Toxic effect of carbon monoxide N
T60.9 Toxic effect: pesticide N
T65.9 Toxic effect: unspecified substance N
T66 Effects of radiation N
T67.9 Effect of heat and light N
T71 Asphyxiation N
Y14 Poisoning by and exposure to other and unspecified drugs, medicaments and biological substances, undetermined intent N
Y17 Poisoning by and exposure to other gases and vapours, undetermined intent N
Y25 Contact with explosive material, undetermined intent N
Z20.9 Contact with and exposure to unspecified communicable disease N
Z29.9 Prophylactic measure N
Cutaneous/lymphatic B05.9 Measles Y
B09 Viral exanthema Y
L02.9 Cutaneous abscess, furuncle and carbuncle Y
I88.9 Nonspecific lymphadenitis N
I89.1 Lymphangitis N
L03.9 Cellulitis N
L13.9 Bullous disorder N
L25.9 Unspecified contact dermatitis N
L29.9 Pruritus N
L50.9 Urticaria N
L51.9 Erythema multiforme N
L72.9 Cyst of skin N
L97 Ulcer of lower limb, diabetic foot ulcer N
L98.9 Disorder of skin and subcutaneous tissue N
M72.69 Necrotizing fasciitis N
R21 Rash N
R22.9 Localized swelling, mass and lump N
R59.9 Enlarged lymph nodes N
R60.0 Localized edema N
T29.0 Burns of multiple regions N
T30.1 Burn of first degree N
T30.2 Burn of second degree N
T30.3 Burn of third degree N
Gastrointestinal A05.9 Bacterial foodborne intoxication Y
A09.9 Gastroenteritis Y
B19.9 Viral hepatitis Y
K29.7 Gastritis N
K29.9 Gastroduodenitis N
K51.9 Ulcerative colitis N
K56.7 Ileus N
K65.0 Acute peritonitis N
K72.9 Hepatic failure N
K92.9 Disease of digestive system N
R10.4 Abdominal pain N
R11.1 Isolated nausea N
R11.3 Nausea with vomiting N
R17 Jaundice N
Hemorrhagic D65 Disseminated intravascular coagulation (DIC) N
D68.9 Coagulation defect N
D69.6 Thrombocytopenia N
D75.9 Blood disease N
I62.9 Intracranial hemorrhage (nontraumatic) N
K92.0 Hematemesis N
K92.2 Gastrointestinal hemorrhage N
R04.0 Epistaxis N
R31.8 Hematuria N
R58 Hemorrhage N
Infectious A39.2 Acute meningococcaemia Y
A21.2 Pulmonary tularaemia Y
A00.0 Cholera due to Vibrio cholerae 01, biovar cholerae N
A00.1 Cholera due to Vibrio cholerae 01, biovar eltor N
A00.9 Cholera, unspecified N
A01.0 Typhoid fever N
A01.1 Paratyphoid fever A N
A01.2 Paratyphoid fever B N
A01.3 Paratyphoid fever C N
A01.4 Paratyphoid fever, unspecified N
A02.0 Salmonella enteritis N
A02.1 Salmonella sepsis N
A02.2 Localized salmonella infections N
A02.8 Other specified salmonella infections N
A02.9 Salmonella infection, unspecified N
A03.0 Shigellosis due to Shigella dysenteriae N
A03.1 Shigellosis due to Shigella flexneri N
A03.2 Shigellosis due to Shigella boydii N
A03.3 Shigellosis due to Shigella sonnei N
A03.8 Other shigellosis N
A03.9 Shigellosis, unspecified N
A15.0 Tuberculosis of lung, confirmed by sputum microscopy with or without culture N
A15.1 Tuberculosis of lung, confirmed by culture only N
A15.2 Tuberculosis of lung, confirmed histologically N
A15.3 Tuberculosis of lung, confirmed by unspecified means N
A15.4 Tuberculosis of intrathoracic lymph nodes, confirmed bacteriologically and histologically N
A15.5 Tuberculosis of larynx, trachea and bronchus, confirmed bacteriologically and histologically N
A15.6 Tuberculous pleurisy, confirmed bacteriologically and histologically N
A15.7 Primary respiratory tuberculosis, confirmed bacteriologically and histologically N
A15.8 Other respiratory tuberculosis, confirmed bacteriologically and histologically N
A15.9 Respiratory tuberculosis unspecified, confirmed bacteriologically and histologically N
A20.2 Pneumonic plague N
A36.0 Pharyngeal diphtheria N
A36.1 Nasopharyngeal diphtheria N
A36.2 Laryngeal diphtheria N
A36.3 Cutaneous diphtheria N
A36.8 Other diphtheria N
A36.9 Diphtheria, unspecified N
A40.9 Streptococcal infection N
A41.9 Septicemia N
A48.3 Toxic shock syndrome N
A49.9 Bacteremia N
A80.0 Acute paralytic poliomyelitis, vaccine-associated N
A80.1 Acute paralytic poliomyelitis, wild virus, imported N
A80.2 Acute paralytic poliomyelitis, wild virus, indigenous N
A80.3 Acute paralytic poliomyelitis, other and unspecified N
A80.4 Acute nonparalytic poliomyelitis N
A80.9 Acute poliomyelitis, unspecified N
A96.2 Lassa fever N
A98.0 Crimean-Congo hemorrhagic fever N
A98.3 Marburg virus disease N
A98.4 Ebola virus disease N
B03 Smallpox N
B34.9 Viral infection N
R50.9 Fever N
R57.2 Septic shock N
Opioid poisoning T40.1 Poisoning: heroin N
T40.6 Poisoning: narcotics N
F11.9 Mental and behavioural disorders due to use of opioids N
Neurological/muscular A05.1 Botulism Y
A39.0 Meningococcal meningitis Y
A86 Viral encephalitis N
A87.9 Viral meningitis N
F05.9 Delirium N
G00.9 Bacterial meningitis N
G03.9 Meningitis, unspecified N
G04.9 Encephalomyelitis N
G24.9 Dystonia N
G41.9 Status epilepticus N
G44.8 Headache, other N
G51.0 Bell palsy N
G52.9 Cranial nerve disorder N
G61.0 Guillain-Barré syndrome N
G62.9 Polyneuropathy N
G72.9 Myopathy N
G83.4 Cauda equina syndrome N
G83.9 Paralytic syndrome N
G93.4 Encephalopathy N
G95.9 Myelopathy N
G96.9 Disorder of central nervous system, unspecified N
H53.2 Diplopia N
M62.99 Myopathy N
R13.8 Dysphagia N
R26.88 Abnormalities of gait and mobility N
R29.8 Symptoms and signs involving the nervous and musculoskeletal systems N
R40.0 Altered state of consciousness N
R40.29 Coma N
R41.0 Disorientation N
R51 Headache N
R56.88 Convulsions N
Ophthalmological/otorhinolaryngological H16.0 Corneal ulcer N
H10.9 Conjunctivitis N
H16.9 Keratitis, unspecified N
H18.9 Disorder of cornea N
H53.9 Visual disturbance N
H57.1 Eye pain N
H57.9 Disorder of eye and adnexa N
J02.9 Acute pharyngitis N
J03.9 Acute tonsillitis N
J04.0 Acute laryngitis N
J05.0 Acute obstructive laryngitis (croup) N
J05.1 Acute epiglottitis N
R07.0 Pain in throat N
S05.9 Injury of eye and orbit N
Respiratory J06.9 Acute upper respiratory infection Y
U04.90 Severe acute respiratory syndrome (SARS) – suspected Y
J04.1 Acute tracheitis N
J04.2 Acute laryngotracheitis N
J11.8 Flu/influenza N
J18.9 Pneumonia N
J20.9 Acute bronchitis N
J45.90 Asthma N
J69.0 Aspiration pneumonia N
J80 Adult respiratory distress syndrome- ARDS N
J96.0 Acute respiratory failure N
J98.0 Bronchospasm N
J98.9 Respiratory disorder, unspecified N
R04.2 Hemoptysis N
R05 Cough N
R06.0 Dyspnoea N
R06.1 Stridor N
R09.2 Respiratory arrest N
Systemic/dehydration E86.0 Dehydration N
E87.0 Hypernatraemia N
E87.1 Hyponatremia N
E87.6 Hypokalemia N
E87.8 Disorders of electrolyte and fluid balance N
N17.9 Acute renal failure N
R23.0 Cyanosis N
R53 Malaise and fatigue N
R55 Syncope and collapse N
R57.1 Hypovolemic shock N
R57.9 Shock N

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