Communicable Diseases

Communicable Disease Alert and Response During Mass Gatherings


Mass gatherings are events in which large numbers of people come together for a common goal or purpose. A communicable disease outbreak at a mass gathering has the potential to overwhelm the public health system of the community or country in which the mass gathering is occurring. Even when public health and other support services are adequate to detect and respond to communicable disease outbreaks in the community, they may not be able to provide adequate support when there is an influx of large numbers of people (national and/or international). Planning for mass gatherings should therefore include risk assessment for communicable disease outbreaks, and planning for management of those risks.

Risk Asessment

Gatherings of people from within the same country may increase the risk of outbreaks from communicable diseases caused by indigenous pathogens. Gatherings that draw visitors from different nations, regions and cultures, however, have the potential for importation of communicable disease pathogens that are not present in the host community, and which may require public health expertise not normally available. In addition, responses to such outbreaks may require accommodating the needs of populations with differing languages, social norms and customs.

Systematic risk assessment helps identify potential outbreak risks and guides the establishment of realistic risk management goals. Sporting events or rock concerts, for example, may have risks associated with alcohol abuse, drug abuse leading to acute blood-borne infections from unsafe injecting practices, or increased transmission of sexually transmitted infections. The risk management goal in such instances would be reduction of risk by ensuring that prevention measures and counseling services are made available, and that those who are infected receive treatment and support.

Religious and/or faith healing gatherings might attract a significant number of the ill and infirm, some of whom could have communicable diseases with the potential to spread to others. Large religious gatherings place pilgrims in very close contact with one another for days, and can impose potential additional risks (such as sleeping outside and increasing risk of hypothermia or hyperthermia if held in inclement circumstances). These may require ad hoc risk communication strategies (teenagers are generally reluctant to absorb strict guidance); for more information, see the Risk communication chapter. Likewise, gatherings of senior citizens may increase the risk and seriousness of respiratory or other communicable disease outbreaks. Risk management goals at such events would be for the provision of facility-based health care in addition to preventive measures.

Of particular concern are mass gatherings at which food is available. These may require special food services to prevent outbreaks caused by contaminated food, along with—as at all mass gatherings—considerations of water safety and sanitation.

Finally, in addition to assessing the risk of naturally occurring outbreaks, systematic risk assessment will also help identify vulnerabilities that could increase the potential for deliberately caused public health risks that require interaction with security and other government agencies (for more information, see the chapter on Deliberate use of biological agents to cause harm).

The risk assessment framework and methodology for communicable disease outbreaks are provided in the Risk assessment and risk management(Risk Assessment and Risk Management, Risk Assessment, Risk Management) chapter. Some of the specific information required for successful risk analysis in advance of a mass gathering could take the form of a checklist including the following considerations:

  • General Features of the Gathering
    • Age and sex of those likely to participate.

    • Likely number of participants and countries of provenance.

    • Season in which the gathering will occur.

    • Potential insect and animal vectors present.

    • Quality of water and sanitation services.

    • Likely food vendors, if any.

    • Features of the hosting location and venues (e.g. geographic/regional features, climate and weather, relevant language(s), population/ethnic groups, customs/traditions, social considerations, security).

    • Movement of population and visitors, accommodation, displacement or overcrowding.

    • Political, systemic or other vulnerabilities that could lead to deliberately-caused communicable disease outbreaks.

  • Specific Communicable Disease Information
    • Indigenous infectious agents circulating in local populations, and in other populations likely to participate, including relevant animal data (epizootics with human cases).

    • Potentially imported infectious agents.

    • Health intelligence obtained by reviews of available health information (at regional and international level), and from history of outbreaks during previous mass gatherings.

    • Vaccine coverage/immunity levels for common infections controllable by vaccination.

Diseases that are important causes of outbreaks at mass gatherings, based on past experience, include those that are highly infectious and have modes of transmission likely to be enhanced by close person-toperson contact and breaks in safe water supply or sanitation and unsafe foods. Diseases with these characteristics should be considered of high priority during risk assessment.
If risk assessment has suggested political or other vulnerability to deliberately caused outbreaks, links should be planned and operationally tested with agencies dealing with criminality (for more information, see the list of agents with potential for deliberate use in the chapter on Deliberate use of biological agents to cause harm).

Risk Management and Planning

Effective management of risks of communicable disease outbreaks in mass gatherings requires advance planning. The Risk communication chapter describes the risk management process for outbreaks and the importance of identifying outbreaks early, and the importance of responding in a timely manner in order to decrease the size of the outbreak and its consequent morbidity and mortality, and to reduce its social, economic and political costs. For outbreaks in mass gatherings the same requirements hold true, and risk management activities should be planned in order to ensure that the necessary services and resources are available. Risk management during a mass gathering is complicated by high event visibility, which may result in political and media pressure that affects the decision-making process.

In particular, planning for mass gatherings should ensure the following:

  • Surveillance and outbreak alert systems, including a system to manage surveillance information, are established to identify risks or actual outbreaks. If these surveillance systems are not in place before the events occur, interpretation of information will be difficult, because of the lack of baseline data.

  • Health services are adequately equipped to offer preventive services and to deal with an outbreak should it occur, and linked with other services, such as those responsible for personal security, food safety, sanitation and water.

  • Contact tracing/quarantine measures are planned well in advance.

  • Provisions are made for management of dead bodies (see the chapter on Communicable diseases in humanitarian emergencies(Communicable Disease Risk in Humanitarian Emergencies, Communicable Disease Control in Humanitarian Emergencies)).

  • Outbreak communications and counseling capacity are adequate to cope with projected needs (see the Risk communication(the Outbreak Communication Environment, Outbreak Communication Guidelines) chapter).

  • A set of standard operating procedures has been developed that ensures that all involved in outbreak management understand their roles so they can work closely together during the mass gathering.

  • Ensure support to outbreak control after the end of the mass gathering, including assistance to the sick after the event is concluded, and providing information on the risks/outbreaks to relevant other countries and to transport hubs and airline/transport companies taking attendees home.

Finally, a budget should be prepared for any necessary reinforcement in infrastructure or health manpower, and training should be provided to health staff and others as required, in order to ensure adequate detection, investigation and response capacity for potential outbreaks.

Legacy of Planning

Care should be taken to ensure that planning maximizes the legacy of the mass gathering: while some investments made during the planning phase may be beneficial only for the duration of the mass gathering, others will provide permanent benefit to public health infrastructure.

Since the investments may be costly, decision makers should clearly understand which lasting benefits will result, and ensure that investment in advance will prevent greater, non-necessary cost in future, should an outbreak occur.

Surveillance and Outbreak Alert

Planning for communicable disease surveillance should preferably build on pre-existing routine systems for infectious diseases surveillance and notification. Surveillance should already be in place to provide baseline data, and systems should be based on case definitions of the indigenous and/or potential imported disease risks identified, while at the same time ensuring detection of other events should they occur. It should be pro-active, and preferably based on an electronic platform so that communication can occur as rapidly as possible.

A major component of alert systems is an event management system that provides the electronic platform, electronic tools, and procedures required to manage information about communicable diseases in a format permitting verification, risk assessment, and data management in a single, reproducible process. Processing of information during the daily routines of the mass gathering, including information protection and its necessary distribution, should also be planned and tested.

Public health laboratory support is vital to surveillance. Laboratories should be capable of identifying known pathogens, especially those circulating in the country where the mass gathering is held and among populations that may travel to the mass gathering from other geographic and climatic areas. They should also maintain valid internal and external quality control, and have provisions for safe and reliable transport and storage of samples, with a capacity that exceeds normal demands.

In the absence of suitable national laboratories, an international laboratory should be identified that can provide the relevant training and/or services, and guidelines for the transfer of specimens between laboratories.

The international transit of large numbers of travelers may require the host nation to report under the International Health Regulations (2005). Instances in which this may be necessary include:

  • Those concerning relevant domestic and international detection and reporting requirements for the host nation.

  • Those concerning the quarantine, surveillance, inspection and medical examination rights and reporting obligations of other states that may be receiving international travelers or transport from the host nation.

For more information on the International Health Regulations, see the dedicated chapter.

Health Services

The tasks of ensuring prevention and patient management services require robust health services. Some of the specific aspects required in such services could take the form of a checklist including the following considerations:

  • Quality first line prevention and patient management services, including counseling.

  • Number of emergency medical staff.

  • Geographical proximity to the mass gathering site.

  • Sufficient surge capacity.

  • Transport to other medical facilities.

  • Supplies for prevention.

  • Medicines or vaccines that correspond to potential risks.

  • Reliable diagnostic laboratory support.

  • Safety of water supplies, sanitation and food.

  • Sustainability for the duration of a potential outbreak or during a prolonged period of heightened alert.

  • Availability of language interpreters/experts on other cultures if gathering is international.

  • Capacity for rapid mobilization of equipment, infection control messages and use of fact sheets and tools (these may need translation).

  • Capacity to supply and quickly distribute potentially large quantities of supplies (e.g. blankets, food, clothing) safely and securely.

Functions that the health services should provide in addition to outbreak investigation include patient management and outbreak containment, and are described more fully in other chapters. Certain of these functions—such as infection control, contact tracing, quarantine, management of dead bodies and outbreak communication—are, however, of a different magnitude and complexity when outbreaks occur in a mass gathering. The following section describes these functions more fully in the context of mass gatherings.

Infection Control

Increased numbers of people seeking medical care during a mass gathering may result in breakdowns in infection control procedures and capacities, especially when personnel resources are stretched. Infection control measures (see also the chapter on Infection prevention and control(Health Care Facilities, Antimicrobial Resistance)) may be necessary at health posts, venues, accommodations, hospitals and other medical facilities where large-scale isolation of patients may potentially be required following an outbreak of infectious disease, as well as in transport hubs, at airports, on buses and trains, and so on.

It is important for public health professionals in such scenarios to protect uninfected patients and contacts housed in common settings. Demographic factors such as language and culture also impact infection control at medical facilities when visitors seek and/or receive care. A vital part of control of disease outbreaks in mass gatherings is the provision of information about the outbreak and disease avoidance procedures to those visitors who are uninfected or asymptomatic, and the problems of language and culture should be taken into account when planning this part of the process.

Contact Tracing/Quarantine

Contact tracing and quarantine measures such as fever surveillance (daily checking for temperature by contacts) require close links with the following:

  • Air and other types of public transport systems, and their hubs.

  • Hotels, hostels, boarding houses and camping grounds.

  • Diplomatic missions and embassies if participants or other patients have come from other countries.

  • Law enforcement authorities, to help locate and identify contacts.

  • Systems and records detailing people's movements.

As part of the planning process, all these should be linked together, with agreements prepared in advance for their mutual operation in the event of an outbreak.
Contact tracing could in some instances lead to the need for mass drug or vaccine prophylaxis, and plans and supplies for mass prophylaxis should also be developed based on the outcome of the risk assessment (see the chapter on Mass vaccination in public health for further information).

Management of Dead Bodies

Dead bodies should be handled as described in the Management of dead bodies section of the Communicable disease control in humanitarian emergencies chapter, and according to the rites and customs prescribed by the relevant religions or cultures. Religious or other leaders who could perform these rites should be identified during the planning process. Emergency mortuary facilities may be required, and should likewise be identified during the planning process, as should the availability of pathologists, including those with forensic skills, especially if bodies are not readily recognizable. Some dead bodies will require repatriation involving international transport carriers, and planning should include relevant consultations and agreements in advance.

Outbreak Communication

Outbreak communication at a mass gathering follows the normal procedures described in the Risk Communication chapter. Multiple language capability may be required for international mass gatherings, and this should be planned for in advance. Communication may be especially important in assuring populations at the mass gathering that risks are being dealt with in an effective and rapid manner. Past experiences have shown the need to arrange the feeding of predetermined routine risk management-related information to the press once or twice daily.


A disease outbreak or other health emergency occurring during a mass gathering may lead to an increased demand for psychological support services from those who are affected, and also those who fear they are at risk. Such demand may be magnified if the outbreak is particularly widespread, has severe health impact, or is the result of a deliberate act. Counseling services need to be planned for persons who have been directly affected by disease, or who have been identified as potentially exposed or otherwise at risk; and also for persons not directly affected but nonetheless having an emotional or mental health response that requires psychological support. Examples of the latter group may include friends and family of patients at home, participants not at any known risk, and medical and/or other staff responding to the outbreak.

Religious leaders, counselors and social workers who are available to provide counseling may need to respond by telephone, and may require assistance from organizations such as the International Federation of Red Cross and Red Crescent Societies.

Standard Operating Procedures

Because many different public health and other community/government services are required for a response to a communicable disease outbreak at a mass gathering, planning should include a mechanism to ensure that preparation and response are well-coordinated. In most large gatherings, several operational units and command posts operate contemporaneously, and many of the necessary public health tasks during an outbreak may require decisionmaking at a level with authority over all of them.

Carefully prepared and tested standard operating procedures that clearly outline the role of each of the required services are a good way of assuring coordination, and a pre-established operations center can provide the necessary coordination and command/control required for these procedures. A network of liaison officers in each command post facilitates the information sharing necessary for decision-making in operations centers.

For further information and guidance on the issues contained in this chapter, see:

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