Health Survaillance

Dec 15, 2010

The global population is approaching 7 billion people and, combined with the ease and frequency of modern air travel, this gives rise to a rapidly increased public health risk at major world events. Mass gatherings, as they have come to be called, are largely pre-planned events, held for a limited time and attended by more than 25,000 people. These events can include any number of purposes – political, religious, athletic – and can be attended by, for instance, 300,000 rabid soccer fans at a FIFA World Cup, or 2.5 million pilgrims at the Hajj in Mecca, Saudi Arabia.

Dr Kamran Khan (St. Michael's Hospital, Toronto) implemented a novel, internationally collaborative approach to health surveillance of the 2010 games, based on the fact that air travel can cause the global spread of infectious disease.

There are many public health factors to consider when planning these events. Most obvious are the police presence and the ability to safely accommodate attendees. However, there exists a relatively new, albeit essential, factor to consider in the planning of mass gatherings: public health surveillance.

While mass gatherings typically feature attendees in good health, such public events also present an ideal environment for the amplification and global dissemination of infectious disease. They also increase the incidence of injury. Common health-related issues at mass gatherings include: heat-related illness, drug and alcohol abuse, ­lacerations, head injuries, trampling, viral infections, gastrointestinal and musculoskeletal issues, increased prevalence of asthma, and heightened risk of terrorism.

Public health challenges result either directly or indirectly from the great number of event attendees. The temporary surge in population density increases both the absolute medical case load, and the potential for the spread of infection. High population density yields a heightened opportunity for contact transmission and respiratory infection propagation, as well as the possibility for changes in the epidemiology of sexually transmitted infections.

Another challenge posed by mass gatherings is the ­mixing of citizens from various ecological and environmental disease backgrounds. Visitors are exposed to locally prevalent infections, while locals are exposed to foreign infectious diseases. For instance, the 2006 FIFA World Cup in Germany ran concurrently with a national measles outbreak – posing an added threat to international attendees.

The sheer volume of attendees creates potential strain on infrastructures that have not been built to withstand the dramatic population increase. Heightened demand on existing services also poses issues regarding water quality, food preparation hygiene, sanitation due to portable washroom facilities, as well as safe and secure accommodation for visitors.

Additionally, the grandeur of many large-scale events often garners increased media attention as we have witnessed recently with the Commonwealth Games in India. For this reason, there is increased potential for acts of chemical, biological, radiological, nuclear, and explosive terrorism. Heightened press coverage also yields the potential for what would normally be a minor health incident to have a more ­sub­stantial impact as awareness (and sometimes misinformation) of the issue is amplified.

In the absence of health surveillance for these events, there can be a considerable lag between the outbreak of a significant public health issue and the response of public health officials.

Infected individuals must first present symptoms of an illness. Next, some of these must seek medical advice. Finally, a sufficient number of patients presenting similar symptoms must seek treatment in order for the issue to be reported to public health officials. Furthermore, alerting of public health is contingent on physicians’ acute ability to recognize an emerging trend, as well as on repeated lab tests confirming the presence of disease. Real-time disease surveillance is designed to severely cut the lag time between disease outbreak and public health response.

Health departments in Miami, Indianapolis and Chicago had seperately installed versions of ESSENCE (Electronic Surveillance Systems of Early Notification of Community-based Epidemics) software to track significant public health events in all three regions simultaneously.

Health surveillance is required at mass gatherings to improve rapid detection of health-related issues, but more importantly, to allow for prompt response to prevent the spread or reoccurrence of these events.

Too often, health efforts are reactive, rather than proactive. Through early identification of emerging trends, public health officials can work to prevent further incidents from occurring. This way, the surveillance system functions as a disease prevention and health promotion tool. In the absence of rapid pattern detection, endemic diseases may spread unknown to public health officials, and recognition of an outbreak may come too long after the optimal response time has passed.

Take, for instance, Ontario’s provision of the H1N1 vaccine in fall, 2009. A study conducted by Beate Sander found that the campaign saved 50 lives, prevented 420 hospital admissions, and kept about one million people from contracting the H1N1 flu. Sander noted that if the campaign had been started later, it would not only have been less effective, it also would have been less cost-effective. Therefore, rapid response to disease outbreak in any scenario is of both health and economic importance.

Mass gathering surveillance can involve any number of important factors, all with the aim of increasing situational awareness. ­Surveillance software receives electronic data input from a variety of sources, such as hospital emergency departments. Incoming information can include patient age, gender, symptoms and more. These properties are analyzed by the software, and are compared to historical data to detect abnormal trends. Detected anomalies signal an alert to epidemiologists.

Therefore, effective surveillance requires daily reporting from various sectors of the healthcare system. Reporting from a wide variety of data sources, both conventional and unconventional, ensures that surveillance is comprehensive. Not only is reporting from emergency departments a useful tool, but reporting increased levels of water bottle distribution may signal an impending outbreak of heat-related illness.

Surveillance systems may already be in place at the event’s location; these systems often require alteration for real-time identification of relevant issues. Alterations may include adjusting the frequency of data reporting to the surveillance team, as effective analysis can only be achieved if data is reported on an ongoing basis. For instance, the 2000 Sydney Olympic Games surveillance team increased mandatory reporting from its sentinel partners – including hospitals, laboratories, and schools – from once daily to three times per day during the Games. Such increases in reporting allow for same-day response to relevant issues.

Once data collection and analysis is in place, communication of such information becomes one of the key components of a surveillance system. Information sharing allows collaboration with all sectors of public health to provide a coordinated response to emerging issues. This way, effective and thorough preventative action – such as educational efforts, strategies to prevent crowding, or installation of hand-wash stations – may be taken. Privacy constraints may pose a problem to data-sharing. Communication is therefore most effective if it includes the analysis and interpretation of trends, rather than the raw data itself. A high level of reporting also yields transparency, which can raise the level of trust in the system.

Additionally, increased reporting raises public awareness, which acts as a preventative measure in its own right.

Super Bowl XLI in 2006 between the Indianapolis Colts and the Chicago Bears took place in Miami, Florida, and provides a great example of a collaborative biosurveillance system. Surveillance of Super Bowl XLI ­represents the first time that separate installations of biosurveillance software were integrated into one system. Health departments in Miami, Indianapolis, and Chicago had separately installed versions of ESSENCE (Electronic Surveillance System for the Early Notification of Community-based Epidemics) software, and used information communication to track significant public health events in all three regions simultaneously. The pre-existence of ESSENCE meant that users were already comfortable with the system. This fact, combined with reports between regions omitting raw data, meant setup took less than 24 hours. The successful collaboration and communication between these bio­surveillance systems displayed the potential for inter-jurisdictional disease surveillance tactics.

Surveillance efforts for Super Bowl XLI underscored the advantages of using a ­surveillance system that analyzes trends from a variety of data sources. The system analyzed data from the ESSENCE software, from the Miami-Dade Fire Rescue 911 Call Centre, and from the Biological Warning and Incident Characterization system. It also used school absenteeism information to gain a comprehensive perspective of potential injury or illness stemming from Super Bowl weekend. While no unusual disease outbreaks were detected, the integrated approach to surveillance did prove useful for detecting other notable trends. Surveillance detected increased daily emergency department visits (between 2425 and 2584 visits per day, compared to the previous two month average of 2315), increased respiratory syndrome cases, increased school absenteeism, increased injury from motor vehicle accidents, and found that a quarter of all 911 emergency calls on Super Bowl Sunday were made from inside ­Dolphin Stadium.

Surveillance of the 2010 Vancouver Olympic Games used multi-jurisdictional surveillance, as Super Bowl XLI did, but also showed a revolutionary approach to integrating data from a variety of sources. Drs. Kamran Khan (St. Michael’s Hospital, Toronto) and John Brownstein (Children’s Hospital, Boston) implemented a novel, internationally collaborative approach to health surveillance of the 2010 Games, based on the fact that air travel can cause the global spread of infectious disease. They combined a web-based infectious disease surveillance system, known as HealthMap, with a global air traffic system called BIO.DIASPORA. Updates were received from both surveillance systems on an hourly basis in an effort to identify where attendees were coming from and what diseases they might bring to the Games. Due to its success, a similar system was implemented to monitor the 2010 FIFA World Cup in South Africa.

Khan and Brownstein’s system targeted diseases that are contagious, those involving drug-resistant pathogens, and those involving pathogens that could indicate acts of terrorism. While no major threats to the Games were identified, the potential benefits of combining syndromic surveillance with monitoring international travel were realized. “The capability to integrate knowledge of worldwide air traffic patterns and intelligence from internet-based infection disease surveillance in real time could significantly enhance situational awareness of infectious disease threats,” assert Khan and Brownstein. Additionally, they suggest that international collaboration for health surveillance can foster global cooperation of health officials.

More recently, acute care health surveillance of the G8 summit in Huntsville, Ontario was performed by the Queen’s University Public Health Informatics (QPHI) team, based in Kingston, Ontario. While these summits were attended by fewer than 25,000 people, and thus do not fit the classic definition of a ‘mass gathering’, public health surveillance at these events is necessary due to their high-profile participants.

The QPHI team analyzed data from a variety of sources including the real-time Acute Care Emergency Management system that monitors Emergency Department visit levels, and the Telehealth Surveillance System that monitors calls into Ontario’s Telehealth nurse-based health advice hotline. Based on historical values developed by QPHI, abnormal public health events could be detected by these systems. Additional data sources used by local public health included reporting from temporary accommodation facilities for the events, and environmental health. While some aberrations were detected, no major threats to public health were present during these summits.

Public health surveillance practices have proved effective in identifying disease outbreaks and other relevant issues. However, absence of adequate ­surveillance remains for mass gatherings worldwide, such as the Hajj in Mecca, Saudi Arabia.

Saudi Arabia has made great progress in improving the health of Hajj pilgrims. For one, vaccination against meningitis is now mandatory for all attendees at this religious ceremony. Additionally, travellers from countries known to be infected with Yellow Fever must show proof of receiving this vaccination. If this requirement is not met, individuals can receive the vaccine upon arrival.

However, influenza is among the most common illnesses experienced by the roughly 2.5 million pilgrims, featuring an estimated 24,000 cases of infection per session. Given that attendees travel from many corners of the Earth, and subsequently travel home after the service, this creates a potential for these 24,000 cases to spread globally. Despite this fact, no real-time ­health surveillance takes place at the Hajj.

As health records and data are increasingly collected electronically in the healthcare field, the opportunity for better public health surveillance is growing. Fusion of information from multiple data streams ­creates a more comprehensive picture of disease activity in populations which can be made available to public health decision-makers. As global population continues to escalate toward and beyond 7 billion, real-time, electronic, automated disease ­surveillance will become the gold standard in the mitigation of international disease outbreaks.  

Aaron Wynn is an undergraduate Life Sciences Honours student at Queen’s University, and a research assistant for the Queen’s Public Health Informatics Team (QPHI).

Dr. Kieran Moore is an adjunct Associate Professor of Emergency Medicine at Queen’s University, and the director of QPHI (
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