A mass gathering has been defined by the World Health Organization as a planned or unplanned event at which the number of attendees is “sufficient to strain the planning and response resources of the community, state, or nation.” Fortunately, the strategies needed to address the public health challenge represented by mass gatherings have rapidly evolved in recent years, but emerging threats such as pandemic diseases and terrorism have further complicated the challenges of preparing for such events.
In areas with little infrastructure, a mass gathering could be fewer than 1,000 people. In major metropolitan areas, the gathering may be in the hundreds of thousands. In other words, from a public health perspective, a mass gathering is comparatively defined and depends upon the local public health and medical infrastructure.
The first step in defining the public health security needed for such an event is a public health risk assessment. It is imperative that the organizers of mass gathering events work closely with local healthcare and public health officials to ensure that health risks are or can be mitigated. A variety of issues must be considered through an event risk-assessment, including but not limited to the local healthcare and public health infrastructure, attendee demographics, and the event’s location, purpose, date, duration, and size. The availability of accommodations and the transportation requirements of attendees also are important factors to consider in the assessment.
Mass Gatherings and H1N1
The spread of the current H1N1 influenza virus provides a timely example of the public health challenges involved in mass gatherings and in the risk assessment factors associated with such gatherings. During a pandemic, major events may have to be canceled or postponed because of the influenza risk involved. The cancellation decision may be based solely on the lack of healthcare capacity in or close to the area where the event is to take place. If hospital beds are already limited, the hosting of a large gathering may impose an excessive burden on local healthcare resources.
In the case of H1N1 threats, this factor is particularly important when the event involves large gatherings of children and/or young adults. Many of the 2009 H1N1 cases reported, in fact, were directly associated with the congregation of young people – at summer camps, for example, and immediately after the recommencement of school in the fall.
The timing of a mass gathering event also is critical and, usually, the most difficult factor to assess in relation to a pandemic. If an event starts during a pandemic wave, the resulting patient surge may overwhelm local healthcare facilities. On the other hand, if the event lasts only a day or two, infected attendees may incubate the disease until they return home and the end result is greater dispersion of the disease. These are all important factors to consider in the development of a mass gathering H1N1 risk assessment.
When a mass gathering event is already underway during an existing or imminent pandemic outbreak, measures must be taken to mitigate the spread of disease. Most importantly, public health messages should be widely shared through announcements, posters, handout materials, and other means. These precautions are basic influenza prevention messages that do not change for mass gatherings. Those who are ill should avoid being in or around crowds of people; all attendees and participants should understand, and practice, appropriate cough and sneeze etiquette, and frequent hand washing should be not only encouraged but actively enabled through the provision of hand washing facilities – supplemented, if possible, by waterless hand sanitizers.
In addition, event organizers should establish locations where those experiencing the early signs of illness may be isolated and assessed. Those locations should preferably be equipped for remote viewing of the event to encourage this alternative participatory option for those with a suspected illness.
The key to effective public health security at mass gatherings is collaborative planning focused specifically on: (1) surveillance and monitoring; (2) health promotion; (3) environmental health and safety; (4) medical care and countermeasures surge capabilities; and (5) the threats posed by infectious diseases.
Mass Gatherings and Terrorism
Special public health preparedness consideration is also made for events that have increased potential to draw the attention of criminal or terrorist activities. These officially designated National Special Security Events (NSSEs) range from sporting events such as the Olympic Games or Super Bowl to political events including but not limited to the presidential inauguration, political conventions, and state funerals. Based on the size and significance of the event, as well as the anticipated attendance of dignitaries, an event may be designated as an NSSE. When that designation has been assigned, the U.S. Secret Service assumes lead agency responsibility and the actions taken usually include additional public health and medical preparedness measures. Those measures often focus on enhanced air monitoring, epidemiological surveillance, the pre-placement of medical countermeasures, and additional planning for patient decontamination and the surge capabilities available in the local healthcare system.
Air monitoring is a particularly important tool to help ensure public safety during large gatherings. The BioWatch Program now in place across most major U.S. cities provides early detection of pathogenic organisms. However, that program is limited both in its coverage area and in the types of organisms that might be detected. In addition, if a covert release is carried out near a building’s air intake system, and/or in a location not in close proximity to a detector – or during a thermal inversion or other weather phenomenon – it could easily be missed by BioWatch detectors. (There also could be a delay in obtaining results from BioWatch monitoring, because filters must be collected and tested daily.)
New technology has emerged that provides a portable chemical, biological, and radiological detection capability in and around key facilities. Although this technology is rapidly evolving, it still has limitations. For example, most information from standoff biological-threat air monitoring is not yet actionable. In recent history, moreover, there has been a series of false-positive biological threat results at NSSEs. As long as biological air-monitoring information is unreliable, the preparations for dealing with a biological threat will pose difficult challenges for decision-makers at mass gatherings.
Epidemiological surveillance includes a variety of approaches. The methods, models, and procedures for effective surveillance at mass gatherings also continue to evolve and expand in scope. Syndromic surveillance is commonly used for NSSEs and includes the monitoring of selected illness syndromes – e.g., fever, respiratory infections, gastrointestinal illness, dermatological presentations, and neurological conditions. These syndromes may be particularly useful in detecting the early onset of mass illnesses resulting from the intentional release of a chemical or biological agent. The information developed must be carefully examined, though, in the context of intelligence, detector results, and other factors to devise an appropriate response.
Assurance of effective public health security at mass gatherings requires coordinated and collaborative planning. The composition of the planning team usually will depend upon the size, scope, and location of the event, but should always include representation from local public health and healthcare agencies as well. The surveillance and monitoring tasks may range from the monitoring of Emergency Department visits to much more elaborate epidemiological and environmental monitoring. Basic environmental health and safety needs include, but are not necessarily limited to, the availability of adequate latrines and hand washing facilities; transportation and food safety, as well as weather threats, also must be taken into consideration. Surge planning for medical care and countermeasures must be tailored according to the population, with special focus on current and emerging infectious disease threats such as pandemic influenza. Finally, healthcare promotional messages should be incorporated into the overall communications plan to keep appropriate prevention messages evident to attendees as well as participants at special events.