Chemical, biological, radiological, nuclear, and explosives (CBRNEs) preparedness for sporting event mass gatherings: A systematic review of the literature

Abstract

Objective:

Sporting events often constitute mass gatherings (MGs) featuring large crowds of spectators and participants. Our objective is to understand the current state of emergency preparedness for sporting events by examining past MG sporting events to evaluate mitigation, preparedness, response, and recovery against chemical, biological, radiological, nuclear, and explosive (CBRNE) events.

Methods:

In accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, a systematic literature review was carried out among 10 literature databases. The quality and risk of bias in each reviewed publication was assessed using the Mixed Methods Appraisal Tool.

Results:

A total of 5,597 publications were identified. Of these, 81 papers were selected for full text reads and 25 publications were accepted. The included articles documented sporting events worldwide, ranging from incidents occurring from 1972 to 2020. Cross-cutting themes found in best practices and recommendations were strategic communication, surveillance, planning and preparedness, and training and response.

Conclusion:

More evidence-based guidelines are needed to ensure best practices in response and recovery for CBRNE incidents at sporting events. Public health risks as well as implementation barriers and opportunities to prepare for potential CBRNE threats at sporting event MGs require further investigation.

Introduction

Events in which people are intentionally using or accidentally exposing others to chemical, biological, radiological, nuclear, and explosive (CBRNE) elements at sporting events constitute a serious, unique threat to the general public. For example, multiple professional and amateur sporting organizations ceased or curtailed events to mitigate the impacts of the COVID-19 pandemic on athletes, staff, and spectators. COVID-19 constitutes a biological agent and is one of a number of threats that have the capacity to significantly alter the way we participate in, spectate, schedule, and market major sporting events. Sporting events often constitute mass gatherings (MGs) as they feature large crowds of spectators and participants. CBRNE preparedness, mitigation, response, and recovery are key elements of mass gathering medicine (MGM).¹ Key features of MGs that have been well-recognized include environmental conditions (temperature and humidity), duration of the event, whether the event is indoors or outdoors, whether the crowd is seated or mobile within the venue, if the event is bounded or unbounded, the type of event, the mood of the crowd, availability of alcohol or drugs, the crowd density, the geography of the venue, and the average age the crowd.¹

Overcrowded sporting events can lead to the rapid spread of infectious diseases or mass casualties in the event of a CBRNE attack. MGs at sporting events are potential targets for terrorists using CBRNE action, as exemplified by bombings at the 1996 Atlanta Games, the 2013 Boston Marathon, and the 2015 Stade de France football (soccer) match. With the focus of the world on a particular event, the venue is tempting for terrorist groups to carry out disruptive acts in order to bring attention to their cause or plight.² These types of international sporting events potentially include thousands of athletic participants, millions of onsite spectators, and billions of television and internet viewers world-wide.³ In addition, accidental exposures to these threats might include industrial spillage of toxic chemicals or spectators harboring contagious diseases.

Despite the significant history and impact of CBRNE incidents at MG sporting events, we have a limited understanding of key themes and best practices to mitigate, prepare, respond, and recover from incidents. Therefore, our objective of this systematic review was to understand and categorize key CBRNE MG sporting event preparedness, mitigation, response, and recovery from recent peer-reviewed literature.

Methods

Search strategy

A systematic literature review was carried out in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.⁴ Manuscripts were considered if found through searches of the following literature databases: Web of Science, Scopus, and EBSCO host (specific indexes of SPORTDiscus, PubMed/MEDLINE, Education Source, ERIC, Rehabilitation and Sports Medicine, Family and Society Studies Worldwide, and Health Business Elite). The search efforts were conducted on October 21, 2020 and on March 28, 2021 to account for recent publications. A publication cutoff date of March 2021 with no start-date limit was used. The keywords for the literature search were based on the stem words of training AND emergencies AND sporting events, AND CBRNE (Table 1).

Table 1.

Keywords used for database searches

Key stem words	Preparing and training	Crisis and emergencies	Sporting event	CBRNE
Specific terms used	prepar* OR train* OR admin* OR manag* OR polic* OR intervention*	crisis* OR emergenc* OR securit* OR disast*	sport* OR arena* OR stadium*	CBRN* OR explosive* OR defen* OR terror*

Articles were included if they were peer reviewed, written in English, included specific information unique to a sporting event, focused on the topic of CBRNE threat or at least one of the included threats and had a description of its preparedness, training or additional response measures to a sporting event including standard guidelines. Following methods of systematic review under PRISMA guidelines,⁴ we mechanically screened titles and abstracts from numerous publications found in the keyword search to include a selected number of fully read papers pertinent of the research literature question. A CBRNE threat was defined as the uncontrolled release of chemicals, biological agents, or radioactive contamination into the environment or explosions that cause widespread damage.⁵ These threats could be introduced by terrorists but we still allowed for accidental exposures to these threats, eg, spillage from a truck transporting toxic chemicals or spectators unknowingly carrying infectious diseases.⁵ A sporting event was defined as an event with an official organization providing the venue and lending support to a competition involving physical exertion or athletic skill. There was no restriction on the size of the sporting event or the duration of the event. We excluded any MG of noncompetitive sporting activities at a venue, such as political or religious MG events. We only included sport gatherings if the publication included a specific year and location for such sporting events which the authors are discussing. We acknowledged the ambiguity inherent in these definitions and allowed inclusion of articles that include primary, secondary, and tertiary information sources, if the manuscript discussed management policies and training practices of CBRNE threats at the given sporting event.

Publications were screened by three authors (SP, KB, and JN) who read the abstract or summary to remove duplicates, non-English papers, papers that did not discuss one or more specific CBRNE threat at a sporting event, and papers that did not discuss mitigation or preparation strategies or give guidelines. Potentially relevant publications were read and critiqued in full. Any dispute with acceptance of papers was discussed with the senior author (TE) who served as final decision-maker. The references cited in accepted papers were also combed for potential inclusion and as additional sources of information.

Critical appraisal

The quality and risk of bias in each reviewed publication was assessed using the Mixed Methods Appraisal Tool (MMAT).⁶ The MMAT was chosen because of its application in assessing quantitative, qualitative, and mixed methods studies, which preliminary searches indicated that all three methodologies are likely to be represented in the articles included in the review. The MMAT has been tested for reliability in systematic reviews and found to fairly assess the quality and bias of each manuscript, specifically examining the control of confounding factors; completeness of outcome data; minimization of selection bias; representativeness of sample; appropriateness of measures; response and withdrawal rates; appropriateness of study design to answer the research questions; and consideration of limitations.⁷ Articles were not removed from the review on the account of low-quality scores because the review aims to assess the existing evidence of prevention and mitigations of CBRNE threats at past sporting events. Therefore, low quality of evidence found in our review would be a finding in itself. All included papers underwent quality assessment by two authors (KB and SP) independently, and any disagreements on study quality were resolved by discussion with coauthor (JN).

Data analysis

An evidence table was created from included articles, extracting the following from each selected publication: each publication’s advice for mitigation, preparedness, response, and recovery from CBRNE, main sporting event(s) discussed, year of sporting event discussed, country of sporting event discussed, and CBRNE threat type. Thematic analysis was used to categorize common management and training topics discussed about CBRNE threats at sporting events.⁸

Results

Overall search strategy findings

Figure 1 shows the results of the search strategy. Overall, we identified 5,597 publications. Of these, 81 papers were selected for full text reads, and 25 publications were accepted in this review. The included papers mentioned sporting events worldwide, ranging from events occurring in 1972–2020 (Table 2). Of these papers, 15 (60 percent) were solely about events where English is the official language. The majority of the papers addressed CBRNE threats at the Olympics and Paralympics, while the remaining featured the FIFA World Championship, the Super Bowl, The Pan-American games, marathons and triathlons, and hockey games. Only one article had recommendations for the sporting event organizers, while the others provided advice for the government or health services. Of the CBRNE threats, five (20 percent) papers discussed chemical threats, 17 (68 percent) were biological, five (20 percent) were nuclear or radiological, and 12 (48 percent) described explosives. The vector of terrorism or terrorist threat using CBRNE was discussed in 12 (48 percent) publications. Because CBRNE threats and sports include a wide array of preventative measures, the papers had widely different suggestions for CBRNE preparation and threat prevention.

Figure 1.

PRISMA flow diagram of search methodology.

Table 2.

Summary and recommendations from included publications

Reference no.	Country/countries	Main sporting event(s) discussed	Year(s) of sporting event discussed	CBRNE threat type(s)	Recommendations given for training, management, planning, surveillance, communications, and strategies
9	Dominican Republic	Pan-American Games	2003	Chemical, biological, radiological, explosives, terrorism broadly	Advocate integrated tactical and medical strike teams as well as use of surveillance tools Extensive preplanning must be conducted
10	United Kingdom	Olympics	2012	Explosives, terrorism broadly	Use of standardized Olympic security model Acknowledge model does not suit all contexts
11	Brazil	Olympics	2016	Explosives, terrorism broadly	Advocate using multicriteria decision support-constructivist approach when designing a system capable of integrating security forces and ensuring the public’s safety Share information from meetings to stakeholders Use strengths, weaknesses, opportunities, threats matrix to identify strengths and weaknesses
12	Greece	Olympics	2004	Biological, terrorism broadly	Advocate using the Pulsar technique when conducting syndromic surveillance to detect biological threats
13	UK, Iran, Germany, USA, Greece	Olympics	2012	Chemical, biological, radiological, nuclear, explosives	Plans need to predict crowd behavior Resources toward hospitals rather than scene of CBRNE incident Training population and medical personnel in CBRNE response Fixed decontamination stations International CBRNE committee Exercise test plans, day or night drills
14	USA	Marathon	2013	Explosives, terrorism broadly	Emphasize that healthcare facilities perform gap assessments Emphasize importance of reevaluation, training, and preparation
15	USA	Olympics	2002	Biological	Culture of cooperation helpful for preparation of surveillance system Negotiations around health data sharing were time consuming
16	USA	Marathon	2013	Explosives, terrorism broadly	Information systems in healthcare facilities were the greatest bottleneck High volume of communication after incident Highly flexible and collaborative leadership structure across institutions led to successful response
17	Australia, USA	Olympics	2000	Biological	Surveillance for bioterrorism and infectious disease Cooperation between public health and intelligence committee effective communication
18	UK	Olympic and Paralympic Games	2012	Biological	Use of surveillance effective Could use online reporting tool
19	Germany, USA, UK, China, Australia, Brazil	Olympics	1972, 1976, 1996, 2008, 2012	Explosives, terrorism broadly	The authors advocate for awareness of terrorism and antiterrorist technology Training in customs matters CCTV Surveillance Cyber security Stop and search authorization Redevelopment programs
20	UK	Olympics	2012	Chemical biological radiological nuclear explosives terrorism	Use of computer simulation in planning to examine potentially dangerous scenarios Training to prepare for threats
21	UK	Olympics and Paralympic Games	2012	Biological	Surveillance tool effective 2-Year planning essential International trainings Surveillance models not universally applicable
22	Australia	Olympics	2000	Biological, terrorism broadly	Carefully planning, comprehensive coverage of public health issues Timely reporting and communication process contributed to the success of public health surveillance The future system needs to be flexible enough to detect unexpected incidents Detailed planning for the surveillance system started roughly 3 years before the games Automated production of reports allowed for more time for analysis Clearly defined communication structure helpful Emergency department be issued with influenza diagnostic kits in future events
23	Greece	Olympics	2004	Radiological, nuclear	Physical protection of nuclear facilities Improved response training Improved threat assessment
24	USA	Hockey games	2008	Explosives	Use of multiple technologies and systems to detect explosive threats Tests such as vendor acceptance tests, integration tests, scoping tests, and countermeasure characterization Larger crowds created blocking effects for the surveillance technology
25	Worldwide	Sport megaevents	2020	Biological	Because volunteers constitute a large part of preparation for events, they must be considered part of security management
26	UK, USA, Australia, Singapore, Greece, China	Olympics and Paralympics	2012	Chemical, biological, radiological	Collaboration and planning to identify threats Reassuring government and media there is not health incidents Robust communication Information brought to a single point Wide range of sources for surveillance system
27	USA	Super Bowl	2019	Biological, terrorism broadly	Utilized the 6 E framework for security preparation and advocated for its use for other events Public health actors need to have explicitly clarified roles before the event and need to have effective partnerships Advocate tabletop exercises
28	Russia	FIFA world championship	2018	Biological	Utilize legal documents to see safety requirements Stop actors working with infectious agents before the games
29	Brazil, Italy, USA, Indonesia, West Africa, Thailand, Micronesia, Philippines, Easter Island South-Pacific	Olympics	2016	Biological	Zika specific advice for travelers to the Olympic games Precautions recommended regarding hygiene, standard, and contact behaviors
30	USA	Olympics	1996	Chemical, biological, explosives	Prioritization of potential threats Training in recognition and treatment of CBRNE threats Use existing infrastructure Preparatory plans and policies Need resources to conduct epidemiological investigation Aid from specialists in CBRNE required
31	Japan	Sports festival and Olympics	2013 and 2020	Biological	Surveillance allowed for earlier response Allow for government to be in contact with necessary parties
32	Australia	Olympics	2000	Explosives, terrorism broadly	Cost of surveillance and security measures in rights and privacy
33	USA	Marathon	2013	Explosives, terrorism broadly	Use of unified command structure for response Need to understand dangers specific to the race (weather, number of runners) Training of staff and volunteers Ensuring proper supply Ensuring multiple lines of communication

Critical appraisal results

Appendix tables A, B, and C summarizing quality assessment for each included paper in this review were given with checkmark, indicating that the respective paper satisfies the question (blank space indicating a “cannot tell” or “no” to each question). Overall, most publications had clear research questions and presented some data, typically secondary or tertiary data to support their research question. Five articles were found to fully satisfy each assessment question of MMAT and 10 publications were found to satisfy all but one question. In many of the papers, there was shortcoming of not having a clear and explicit description about their presented data. This is a methodological concern for findings in this review due to potential bias and confounding factors that may be attributed to the prescriptive recommendations given by included publications. Table 3 describes cross-cutting themes and best practice recommendations. The following sections further describe these thematic findings.

Table 3.

Themes and summary of best practices

Cross-cutting themes	Summary of findings and best practices
Strategic communication	Need to ensure stable lines of communication between different responding bodies (emergency services and hospitals) Clearly defined communication structure was useful Multiple lines of communication important Highly flexible and collaborative leadership structure lead to a successful response Prepare for a high volume of communication after an incident Need to advocate for multicriteria decision support as a constructivist approach when designing a system capable of integrating security forces and public safety
Surveillance	A wide variety of surveillance techniques and technologies based on different threats Surveillance can allow for earlier responses When surveillance involves a variety of organizations, there must be effective collaboration Surveillance systems must be properly designed for the event as some are less effective with large crowds
Planning and preparedness	Simulations can be highly effective for planning All involved organizations must work together in planning Advocated extensive preplanning Information system disruptions in healthcare facilities need to be tested regularly, as they can create significant bottlenecks Plans need to predict crowd behavior Need to understand the potential dangers specific to the event taking place
Training and response	Importance of training personnel in CBRNE response emphasized widely across articles Test plans, with day/night practice drills

Discussion

Security threat assessment is vital for managing the health risks of the deliberate use of biological, chemical, radiological, or nuclear agents.² Although it is challenging to ensure complete security in all cases against CBRNE threats, the studies we reviewed sought to mitigate the threat of CBRNE incidents at major sporting events. The findings of the papers in our review align with pre-existing North American Treaty Organization (NATO) guidelines regarding CBRNE incidents in terms of planning, preparedness training, infrastructure, surge capacity, proper personal protective equipment (PPE) while maintaining adequate stockpiles of antibiotics, vaccines, and antidotes.³⁴ Few published studies we reviewed were focused on how to respond at the scene of a CBRNE incident with subsequent scene management and specialist support.^13,20,30 The majority of articles emphasized mitigation and preparedness for CBRNE threats aligning with some practices suggested in NATO and World Health Organization (WHO) reports, but there are still differing approaches and applications.^2,3,34 While the NATO and WHO reports provide overarching general advice, the body of literature we examined gave specific cases and examples based on real world experience as seen in Table 3.

Definitions of mass gatherings

Literature documenting CBRNE threats in MGs often treats different venues as similar, lending perspectives and recommendations that may not be applicable to all types of MG events. Because of this common assumption, we conducted a systematic literature review in order to assess how to what extent prior scientific studies addressed CBRNE threats at sporting events and took into account the features of MGs, which are unique to a sport. Definitions of MGs are limited and may not include all sporting events in mind because they only consider the size of the crowds and are based on a single characteristic of the event rather than on a broader understanding of the phenomenon. A broader definition that accounts to various phenomena caused by the event is useful as it recognizes that planning for and the delivery of health services are complicated by context and situation in which care will be provided.¹ For example, a mass pilgrimage would have different needs than a football championship match.

The perceived threat in some countries has evolved toward increasingly nonconventional means with MGs. The attacks on the Tokyo metro system in 1996 with sarin gas, which killed 14 people, and US postal letters containing anthrax in 2001, killing 5, indicate that terrorist groups have both the intent and the capability to construct novel and carefully planned nefarious acts. Even natural infectious diseases like the plague (Yersinia pestis) have been weaponized.³⁵ The terror associated with reaction to the use of a chemical, biological, or nuclear weapon during an MG can have enormous social and economic consequences, creating a large public health burden, pushing a fragile healthcare system well-beyond its normal surge capacity. This problem is compounded by the fact that more traditional terrorism may engage in the use of conventional (and readily available) explosive devices.

High-profile MGs together with the long-term planning and preparation for these events make them ideal targets for terrorists to infiltrate and publicize their particular cause. The large numbers of spectators attending MGs with overcrowding beyond capacity and little space for rapid evacuation places strain on the host country’s infrastructure, making MGs particularly vulnerable to CBRNE attacks.³⁶

Additionally, CBRNE threats can come from accidental exposure as well. Incidents such as industrial chemical spills or unintentional transmission of infectious agents at sporting events are just as potentially dangerous as terrorist attacks. Pandemics like COVID-19 can be amplified well after the sporting competition when participants cross international borders, travel globally, and return to their home countries.

Against these threats are a multitude of parties that need to operate in a coordinated fashion to provide security, preparedness, and training. Government agencies, such as police and military personnel, as well as healthcare providers need to act in concert with facilities managers and private organizations who manage sports venues. This coordination can be obscured if there is a lack of effective communication between involved agencies, thereby increasing vulnerability to CBRNE threats. Advanced training exercises that coordinate and facilitate interoperability between international, national, and local actors engaged in countermeasures to CBRNE attacks are critical.³⁷

Sporting events are not the only venues which face CBRNE attacks. Other MGs such as large music festivals, stadium concerts, or religious pilgrimages like the annual Hajj face similar threats.³⁸ Still, the possible unique features found at international sporting events could differentiate from aspects found in general MGM literature. However, there appears to be agreement on the principal goals of mass-gathering medical care that aligns with mass sporting events. These include establishing rapid access to the injured or ill patients, providing triage, effectively and timely stabilizing and transporting seriously injured or acutely ill patients, and providing on-site care for minor injuries and illnesses.¹

Biological threats

To prevent biological threats, articles found in this review discussed the use of surveillance systems. Several publications analyzed the effectiveness of biological surveillance systems designed to track infectious diseases at sporting events.^{9,12,15,17,18,21,22,24,26,29,31} These surveillance systems typically involved the sharing of patients’ deidentified data from medical facilities, so that there could be an overall picture of infectious disease community prevalence. Furthermore, several articles stressed the importance of cooperation and communication in effective surveillance, even involving intelligence committees and other methods of public health interventions for sporting events.^{9,15,17,18,22,26,27,31} For example, biological surveillance was mentioned and predominantly conducted by government agencies in cooperation with healthcare providers. Gesteland et al.¹⁵ mentioned that there was a risk for hospitals associated in providing patient data to these surveillance systems providing this can be balanced with the potential benefits gained by contributing such information.

Chemical threats

There were five articles that mentioned chemical threats but only two gave prescriptive advice that specifically applies for chemical attacks.^{9,13,20,26,30} This can be attributed to the fact that these chemical threats were typically included with the broader CBRNE measures, and many of the chemical and biological preventative measures tend to overlap. For example, in the XIV Pan-American Games, live animals were used in the detection of chemical and biological threats.^9,27 In terms of treatment of both chemical agents and biological threats, they require initiation immediately after exposure, so hospitals need to be stockpiled with adequate PPE and proper antidotes.³⁰ Plans against chemical attacks should be prepared for military grade chemicals, eg, sarin and other nerve agents, as well as readily available harmful industrial chemicals such as ammonia or chlorine gas.³⁰ There must be standard observational criteria or screening procedures in place to recognize a sudden chemical attack or a biological incident, which may not be immediately obvious by observation.³⁰

Nuclear or radiological threats

Five of the articles mention nuclear or radiological attacks, yet only two papers addressed specific steps that must be taken against nuclear and radiological threats. Several studies took the steps of taking inventory of nuclear sources, physical protection of radiological facilities, prevention of illicit trafficking, radiation detection at the venues, cooperation between organizations, and training key personnel involved in the national emergency plan.^{9,13,20,23,26} Báez et al.⁹ mentioned specialized weapons of mass destruction (WMD) units who conducted ionizing radiation monitoring sweeps.⁹

Explosives

One of the chief concerns among articles discussing explosives is the use of surveillance technology to detect explosives.^10,20,24 Knudson et al.²⁴ advocated for multiple technologies to detect threats, and an awareness that large crowds will obscure detection. Johnson²⁰ advocated using software to help train for evacuation planning in the event of an explosion. Toohey and Taylor³² addressed that terrorism and the use of explosives have led to increased securitization, surveillance, and legislation against protest that limits privacy and freedom of demonstration.³² Detecting explosives and counteracting terrorism at mass sporting events have been given priority than individual privacy among attendees.

Gates et al.,¹⁴ Goralnick et al.,¹⁶ and Landman et al.³⁹ raised concerns regarding tracking registration systems being overwhelmed after the terrorist attack at the 2013 Boston Marathon. During that incident, various unidentified naming conventions led to mix ups in ordering lab work and diagnostic imaging. In addition, patients arrived rapidly, and interventions were limited by registration in the electronic health record. Gates et al.¹⁴ raised the prospect of infectious disease complications resulting from airborne viral particles. Most injuries were penetrating blast injuries from metal, ball bearings, and nails from the improvised explosive devices.¹⁴

Mitigation and preparedness planning

The critical importance of preparedness planning was stressed in many of the articles.^{9–11,13,17,20–23,26,27,30} These authors all stressed planning different aspects of CBRNE preparedness such as establishing a surveillance system,^{9,21,22,26,27} planning to predict crowd behavior,¹³ and plans for mass immunization or chemoprophylaxis, evacuation, and public communication.³⁰ Specific planning for potential mass casualty scenarios for marathon staff health officials and government agencies was also presented as well as preparedness for nuclear emergencies.^23,33 Security force integration and the use of computer simulations in planning were further discussed.^11,20 Although a surveillance system could be rapidly set-up, there was a benefit to having 2–3 years to plan especially for larger venues like the Olympic games.^15,21,22 In terms of response, Goralnick et al.¹⁶ emphasized the need to manage an influx of multiple patients at one time, as was the case with the Boston marathon bombings.¹⁶ They found that caring for multiple patients was dependent on the ability of hospital staff to evacuate the emergency department of existing patients, which contributed to the favorable conditions within the trauma units. First responders were also part of the preparedness as they were the initial point of contact to establish scene response and management.¹⁶ Advanced planning, rehearsals, drills, and proper dispersal of causalities were instrumental in dealing with the events of the Boston Marathon bombings.

Preparation and exercise drills

Training was advocated in 10 of the articles.^{9,11,13,20,21,23,24,27,30,33} Galatas¹³ advocated training in CBRNE response for the general public and medical personnel.¹³ They recommend a wide array of training strategies, from tabletop and field exercises to hospital drills with first responders. Other authors advised training for specialists in recognition of treatments of CBRNE threats,³⁰ training visual surveillance operators,²⁴ military troops,^9,11 healthcare providers,^9,27 training using software programs,²⁰ security teams training in nuclear response,²³ training of staff and volunteers,³³ and international trainings for global responses.²¹ The specific details of these training sessions were not addressed in the articles.

CBRNE best practices and recommendations

Overall, the relative scarcity of articles indicates that in order to give specific best practice recommendations, we needed to include outside literature. Using a combination of WHO and NATO reports as well as our literature search, we recommend the following best practices for CBRNE incidents in terms of mitigation, preparedness, response, and recovery of a potential CBRNE incident at a sporting event.

To mitigate biological threats, public health officials, environmental surveillance services, laboratory technicians, and healthcare providers should be vigilant for the delayed occurrence of atypical symptoms or syndromes in a cluster or large number of patients. There needs to be stockpiles of prophylactic antibiotics, vaccines, and antidotes as well as ample supplies of PPE. In addition, law enforcement officers, front-line responders, and security personnel need to be available and on “ready alert” 24/7 during these MG events.³⁵

We found a wide range of authors supporting bio-surveillance in preparation for these types of MG sporting events. Methods of tracking the spread of infectious diseases during and after a full capacity sporting event will be especially critical in the era of COVID-19 once spectators are allowed back into sporting venues. Bio-surveillance requires a coordinated approach and cooperation between healthcare providers, government agencies, and sporting facility operators. In the future, facilities operators will likely need to be more involved in conducting bio-surveillance, so infectious disease tracking can occur before attendants present to local hospitals. Preventative measures such as widespread testing can also begin several weeks prior to the event to ensure that the venue is safe for public access.

There were less articles in our systematic review addressing chemical threats. Nerve agents are fast acting and require rapid response, so it is imperative that facilities have proper PPE and decontamination measures in place at the scene, and that healthcare providers are properly provisioned with antidotes. Governments, health providers, and facilities managers also need to be on alert for accidental industrial exposures just as with deliberate chemical attacks.

Large numbers of symptomatic, critically ill and traumatized victims may be contaminated at the scene of the incident requiring transportation to a medical facility. As with the 1996 Tokyo sarin gas attacks, larger numbers of walking wounded and “worried well” spectators may also present in over-whelming numbers to medical facilities for treatment and reassurance. Medical facilities, public health officials, mental healthcare professionals, and government leaders should be warned of the incident, estimated number of victims, and informed about whether they may be contaminated requiring decontamination prior to entering a healthcare facility or larger public space (such as a mass transit system or emergency shelter). Ensuring that decontamination sites and post-incident medical support are available for rescue and medical staff involved in the incident zone is essential. Also making sure there are methods to decontaminate or quarantine medical facilities and equipment after use with the incident. Rapid triage stations to separate the most critically ill patients with access to nearby decontamination tents with large sources of water will be needed for proper decontamination, together with the means for the safe disposal of the contaminated water.³⁶ Showering facilities for victims and staff should include supplies of clean clothing. Contaminated items will require disinfection, eg, with chlorine, incineration, or burial.³⁶

There were very few articles that specifically addressed how to prevent radiological or nuclear attacks and none that addressed dealing with the long-term aftermath of a nuclear attack. Government agencies need to monitor nuclear inventory and facilities and guard against any illegal transportation of radioactive material or nuclear devices. More work is required to determine which venues need nuclear attack preparedness as well as dealing with the aftermath and fall-out. Scanning event locales with radiological dispersal devices prior to a competitive event are recommended. Coordinating with local authorities to know what the potential radiological/nuclear threat level is within a particular region is important when designing a preparedness plan.

The literature suggests using surveillance programs to detect and track explosive threats. Crowds can complicate accurate surveillance measures; therefore, there is a use for rapid evacuation protocols for athletic participants, and spectators are necessary to implement. Additionally, contingency plans in the event of an explosion must be drawn up with standard mass casualty field triaging exercises with Advanced Trauma Life Support preparedness training to manage and triage multiple victims. Another potential threat is a detonation of a “dirty bomb” or an explosive device intentionally contaminated with radioactive material. Explosives also have the capacity to carry chemical and biological agents, and first responders need to be prepared for potential exposure at the scene.⁴⁰ Trauma care of these victims is similar to other conventional explosive devices, but those who are exposed or walking wounded may experience post-traumatic stress disorders and “radiophobia.”

For all CBRNE incidents, there needs to be MG response plans including procedures for rapid evacuation and decontamination of large numbers of participants. Regularly scheduled preparation activities for efficiency and rapid deployment include disaster drills and tabletop exercises that should be conducted several weeks and months prior to any MG event. First responders, frontline workers, and medical personnel will need to be trained in the use of decontamination equipment and structures of triage systems to prioritize care of the most critically ill (and potentially salvageable) patients. Sufficient stocks of medical equipment and hospital-wide surge capacity must be readily available to meet extreme high-volume situations.³⁶

Overall, preparedness planning was discussed in many of the articles reviewed. However, there was a lack of a unified approach on the reporting of best practices and health outcomes resulting from the preparedness efforts proposed. This may have been caused by the silos of knowledge that are put in place to remain individualistic rather than foster collaboration. Finally, statistical metrics could have been inconsistent due to the lack of clear quantifiable categories present in MG research. Thus, a creation and utilization of a reporting and publication template is a major recommendation.⁴⁰

A new generation of terrorism

A recent phenomenon is the evolution of a post-modern terrorism or era of “super-terrorism.” The goal of this type of terrorism is to send a political message by maximizing the number of casualties.³⁶ Novel weaponized agents with innovative methods of delivery need to be considered. In general, effective dissemination of such agents and material is generally more difficult than their production or acquisition. The technical problems associated with dispersing large quantities are complex and require highly developed organizational capabilities within these super-terrorist groups.² Both domestic and international terrorist threats need to be considered due to their implications.

Response and rapid detection methods

Creation of an organized antiterrorist medical rescue system is critical. Regional medical institutions with specializations in infectious disease, chemical exposures, radiation illness, trauma, and burn management should be established. Reference laboratories are vital for verification and identification of biological agents such as smallpox, yersinia pestis, anthrax, ricin, botulinum toxin, or even weaponized coronavirus (SARS-COV-2) as well as chemical agents, eg, nerve agents, chlorine gas, and radioactive materials. Detection and surveillance systems should include environmental biological particle detectors, chemical sensors, mobile spectrum analyzers, and other rapid spot-detection technologies.² Hospital capacity and intensive care unit availability will be stretched beyond normal limits, so frequent evaluation and monitoring of facility infrastructural surge capacity is necessary.^41,42

Recovery and capacity building

Despite widely accepted international laws such as the 1925 Geneva Protocol, the Biological and Toxin Weapons Convention, and the Chemical Weapons Convention, preventing or countering the deliberate use of biological, chemical, or radiological agents is extremely challenging. Without widespread preparation, most infrastructures—including modern healthcare facilities of most countries—are ill-prepared to prevent and manage a CBRNE incident with multiple causalities. Terrorism events are notorious for sudden, unexpected, unpredictable, and complex attacks.² Rapid assessment, including knowledge of the health effects of biological, chemical, or radiological agents, as well as effective risk communication strategies, health system capacity, and the identification of unusual disease patterns requires calculated preplanning and advanced training. Building capacity in this field is an exercise in interdisciplinary collaboration, shared between public health and medical personnel, emergency and disaster services, law enforcement authorities, military and government ministries as well as private organizations. This is not unique issue for major sporting events as it is a common necessity for building capacity in preparation for all types of MGs. Prevention, training, and mitigation in all countries, even in armed conflict scenarios, need to meet standards for front-line responders.^34,37

Finally, there is also a cost to combating CBRNE threats. Increased security measures can make spectators uneasy or constitute an undue breach of privacy. Additionally, protection measures implemented for events such as the Olympic games have been claimed to unduly deter peaceful public protests.³² A proper balance of security and respect for spectators’ rights needs to be maintained. Additionally, there is a financial cost to security. Smaller events need to work with larger organizations like government or medical services to ensure that they have the capacity to deal with CBRNE threats. Also, countries should consider whether or not they are prepared to deal with potential CBRNE threats when bidding to host larger events, such as the Olympic games.

Future research

We have found that the majority of the sports-related literature on preventing CBRNE attacks focus on the Olympic games. Although the Olympics constitute a major target for CBRNE attacks, there are a wide array of other sporting events such as football (soccer), rugby, and cricket world cups. The National Football League, Major League Baseball, and the National Basketball Association have high visibility events that may be tempting targets for terrorism. Additionally, the differences of sports, eg, amateur versus professional and rural versus urban, may make different events more or less vulnerable. For example, marathons take place in wide-spread areas where it is much more difficult to create a secure perimeter, whereas stadiums contain large crowds within an enclosed area with a greater potential attack impact.

Because most of the studies we reviewed highlighted the Olympic games, the main actors preventing CBRNE threats were government agencies. More studies are needed that address nongovernmental actors involved in CBRNE threat prevention, from sports owners, security, facilities managers, and spectators. The Olympics is a high-profile target that has had terrorist incidents before, such as the 1972 Summer Olympics in Munich; however, other MG sporting events have similar high visibility that would make them vulnerable such as FIFA World Cup. In 2018, the Russian Federation had an increase in terrorist threats at the FIFA World Cup due to Russian Federation’s involvement in the Syrian civil war.⁴³ Other smaller events have been attacked including the 1996 Manchester bombings, 2008 Sri Lankan Marathon, 2010 Uganda World Cup bomb, and the 2013 Boston Marathon. With the recent 2020 Summer Olympics in Japan (delayed to 2021) and upcoming 2022 FIFA World Cup in Qatar, organizing countries and nongovernmental actors should be aware and plan accordingly.

In this review, the included publications provided less theory in prevention, mitigation, and training of CBRNE but offered prescriptive advice and recommendations for MG sporting events. Most of these articles were an attempt to evaluate the success of a specific security measure at a specific event or an overall discussion of what security measures were taken. Future studies drawing from crisis management or public health literature to use theory to inform CBRNE prevention practices are recommended. Most of the knowledge on how to deal with CBNRE threats for sports venues may still be in specific volumes, workshops, trainings, and manuals, which were not picked up in our search, and we recommend that there will be a concerted effort to incorporate this into academic literature. The most immediate CBRNE challenge stems from the COVID-19 pandemic, which has shut down larger crowd spectatorship. Reopening sporting venues will require comprehensive security for spectators that may not be possible without a comprehensive vaccination program. In the meantime, bio-surveillance of the athletic participants and the larger fan-base needs to continue and be improved upon for maximum security.

As described by Arbon,¹ it is appropriate to ask how current mass-gathering knowledge and understanding can be applied across different events.¹ What concepts or models can help us to understand MGs in ways that will contribute to the provision of appropriate services at new events or across different types of events? And what influences and characteristics apply across all or most MGs? Mass sporting events have fundamental similarities with other MGs; however, they also have unique challenges faced among CBRNE threats.

Limitations

Our review has several possible limitations. First, confirmation or selection bias could have occurred when identifying publications for review. To guard against this, we had two researchers review each article, and if a dispute occurred, a third researcher was used as a tiebreaker. Second, it is unlikely that we identified every relevant study in the literature, but we used broad keywords, which provide some reassurance that the inclusion of missing studies would not radically alter the nature of our review.

Although a significant number of articles covered CBRNE incidents, most did not factor in sporting events into their analysis; therefore, our sample size of included articles was small. Sporting events are unique MGs as they can encompass areas beyond traditional venues like arenas, to entire cities, as with marathons. Additionally, sporting events like the Olympics offer world-wide attention for those looking to advance political agendas. Sporting events can be exceedingly international, sometimes with a collision of cultures. Finally, sporting events frequently host historical rivalries that may turn violent. This relative dearth of articles describing CBRNE threats at sporting events demonstrates that the literature deviates from specificity when dealing with MGs, which may, in turn, limit the applicability of findings if they treat all MGs as similar. This relative lack of literature also suggests that knowledge may include specialized materials like workshop notes or training manuals, which are far less conducive to collection within a literature review. The included articles each factored the unique nature of the event or events they covered when considering how to optimally respond to CBRNE threats. We also recognize that there are confounding variables with different MG sporting events. These venues will have different resources available to prepare for and respond to CBRNE threats, as well as variations in susceptibility to these threats.

The critical appraisal tool used is intended for empirical papers; however, we included publications that used primary, secondary, or tertiary data as results or findings. We applied this assessment tool to gauge the quality and risk of bias in each publication. Our appraisal finding is limited due to the wide array of methodologies employed by these studies. Our literature review also had a relatively small sample size narrowing it down from 5,597 being identified to 81 being screened to 25 being included. This is due to the increased specificity of our search criteria and indicates that there is limited peer-reviewed literature on this topic.

Conclusion

The purpose of this systematic literature review was to gather best practices from the academic community to manage CBRNE threats at MG sporting events. Additionally, we sought to uncover areas that may require further academic inquiry. We found best practices addressing past CBRNE threats focused primarily on strategic communication, surveillance, preparedness with training, and response. We found that coordinated planning between governmental, medical, and private stakeholders is essential to properly detect CBRNE threats. This also allows for a more streamlined mitigation in the event of an actual emergency. Additionally, implementation of disaster protocols for rapid response, allowing for ordered and timely evacuation of victims, with proper decontamination and treatment at well-equipped medical facilities is needed. Public health risks as well as implementation barriers and opportunities to prepare for and recover from potential CBRNE threats at sporting event MGs require further investigation. This reflects a need for evidence-based guidelines within the field as there is a lack of a unified approach. In the COVID-19 pandemic era, these coordinated efforts will help ensure major sporting events can be safely conducted for both athletes and spectators.

Appendix A. Summary table of quality assessment for qualitative studies

Reference	S1. Are there clear research questions?	S2. Do the collected data allow to address the research questions?	1.1. Is the qualitative approach appropriate to answer the research question?	1.2. Are the qualitative data collection methods adequate to address the research question?	1.3. Are the findings adequately derived from the data?	1.4. Is the interpretation of results sufficiently substantiated by data?	1.5. Is there coherence between qualitative data sources, collection, analysis, and interpretation?
9	✓	✓	✓	✓	✓	✓	✓
10	✓	✓	✓		✓		✓
11	✓	✓	✓	✓	✓		✓
13		✓	✓		✓		✓
15	✓	✓	✓		✓	✓	✓
16	✓	✓	✓	✓	✓	✓	✓
17	✓	✓		✓	✓	✓	✓
19	✓	✓				✓	✓
20	✓	✓	✓		✓	✓	✓
23	✓	✓	✓		✓	✓	✓
25							✓
26	✓	✓	✓	✓	✓	✓	✓
27	✓	✓	✓	✓	✓	✓	✓
30	✓	✓	✓		✓		✓
32	✓	✓	✓			✓
33	✓	✓	✓				✓

Appendix B. Summary table of quality assessment for mixed methods studies

Reference	S1. Are there clear research questions?	S2. Do the collected data allow to address the research questions?	5.1. Is there an adequate rationale for using a mixed methods design to address the research question?	5.2. Are the different components of the study effectively integrated to answer the research question?	5.3. Are the outputs of the integration of qualitative and quantitative components adequately interpreted?	5.4. Are divergences and inconsistencies between quantitative and qualitative results adequately addressed?	5.5. Do the different components of the study adhere to the quality criteria of each tradition of the methods involved?
14	✓	✓	✓	✓	✓	✓	✓
21	✓	✓	✓	✓	✓		✓
22	✓	✓	✓	✓	✓		✓
29	✓	✓		✓	✓
31	✓	✓	✓	✓		✓

Appendix C. Summary table of quality assessment for quantitative descriptive studies

Reference	S1. Are there clear research questions?	S2. Do the collected data allow to address the research questions	4.1. Is the sampling strategy relevant to address the research question?	4.2. Is the sample representative of the target population?	4.3. Are the measurements appropriate?	4.4. Is the risk of nonresponse bias low?	4.5. Is the statistical analysis appropriate to answer the research question?
12	✓	✓			✓		✓
18	✓	✓	✓	✓	✓		✓
24	✓	✓	✓	✓	✓		✓
28	✓		✓		✓