This scoping review adopted the PCC (Population, Concept, Context) Framework and is reported through the PRISMA extension for scoping reviews (PRISMA-ScR) guidelines published in 2018. PRISMA-P was initially used during protocol development, but the completed review aligns with PRISMA-ScR reporting standards (6).

Three electronic databases (Scopus, ProQuest, PubMed) were searched. Gray literature was retrieved from the World Health Organization’s Institutional Repository for Information Sharing (WHO IRIS) and the Centers for Diseases Prevention and Control (CDC)¹ where the same core concepts (Event-Based Surveillance, epidemic intelligence, mass gatherings) adapted to each platform’s search interface.

A comprehensive Boolean search strategy combining relevant keywords and synonyms using “AND” and “OR” was employed. No time filters were applied during the initial search phase to maximize retrieval sensitivity though English language restriction was done.

Database	Search query
PubMed	(“Event-Based Surveillance” OR “EBS” OR “Epidemic Intelligence” OR “Infectious Disease Monitoring”)AND(“Mass Gathering” OR “Mass Gatherings” OR “Mass Gathering Events” OR “Big Event” OR “Big Events” OR “Hajj” OR “Arbaeen” OR “Olympics” OR “FIFA World Cup” OR “Kumbh Mela”)
ProQuest	(“Event-Based Surveillance” OR “EBS” OR “Epidemic Intelligence” OR “Infectious Disease Monitoring”)AND(“Mass Gathering” OR “Mass Gatherings” OR “Mass Gathering Events” OR “Big Event” OR “Big Events” OR “Hajj” OR “Arbaeen” OR “Olympics” OR “FIFA World Cup” OR “Kumbh Mela”)
Scopus	(“Event-Based Surveillance” OR “EBS” OR “Epidemic Intelligence” OR “Infectious Disease Monitoring”)AND(“Mass Gathering” OR “Mass Gatherings” OR “Mass Gathering Events” OR “Big Event” OR “Big Events” OR “Hajj” OR “Arbaeen” OR “Olympics” OR “FIFA World Cup” OR “Kumbh Mela”)
WHO & CDC	“Event-Based Surveillance” AND “Mass Gathering”

The search was conducted for all fields using the basic search with no filters applied for all databases. Details of the search records, such as the date of the search, database, keywords, number of studies identified, and the number of eligible studies were appropriately documented.

The extracted data were synthesized narratively and thematically covering the core objectives of the review. Findings were organized around the research questions with sections addressing EBS best practices, challenges, geographical patterns, and strategic recommendations.

We conducted a thematic analysis of the included publications identifying patterns using Microsoft Excel. We extracted the main recurring themes under the main domains in our review. Themes emerged from the data through comprehensive reviews allowing for merging and splitting findings when appropriate ensuring a structured synthesis of evidence.

As of March 30, 2025, we identified 1,469 studies, 141 were excluded as duplicates. Titles and abstracts screening for the remaining 1,328 studies resulted in the exclusion of 1,285 studies. The remaining 43 studies were subjected to full-text screening against the eligibility criteria leaving 28 included studies to be included (Figure 1). The study was completed on 27 May 2025.

A detailed data charting table (Supplementary Table) summarizing key extracted variables for all included documents including bibliographic details, MG event type, surveillance duration, signal sources, and verification workflows is provided in Supplementary material.

Among the 28 included records: 14 (50%) were peer-reviewed articles, 12 (43%) were gray literature (WHO reports, bulletins, technical guidance), and others were dissertation/thesis. When classified by document purpose: 11 (39%) were implementation or case-based reports, 5 (18%) were formal evaluations, and 12 (43%) were descriptive or guidance documents.

Among the 28 included studies, Iraq (7–10), Saudi Arabia (11–14), and the United Kingdom (12, 15–17) were the most frequently represented, each appearing in four studies. Japan appeared in two studies (18, 19), while India (5), Qatar (20), Italy (21), Brazil (22), Lebanon (23), Spain (24), and South Africa (25) were each represented once. Several studies addressed multi-country or regional contexts across Europe, the Eastern Mediterranean, Africa, the Caribbean, and the Pacific (26–28). Two studies provided global guidance on EBS during mass gatherings (1, 29).

From the above figures, we can see that 11 studies (39%) came from just three countries (Saudi Arabia, Iraq, and the UK) while regional/multi-country contexts were covered in five studies (18%). Two studies (7%) provided global guidance (Figures 2–4 and Table 1).

Mass gathering Event types are distinguished within the included studies. Most documented events were either sporting events (39%, n = 11) or religious ones (21%, n = 6). Among the sportive events included are Olympic and Paralympic games as featured in five studies from Japan, and UK. This represents international multi-sport events with tens of thousands of participants and extensive international travel. FIFA World Cup Events and Cricket World Cup are also featured in four studies, and one study, respectively. Other sportive events included UEFA Euro 2020 and Francophone Games.

Cultural and political mass gatherings appeared in two studies (7% of the included studies). Example is internally displaced people camps which are featured in one study and it represents a unique mass gathering contexts with distinct epidemiological profiles including concentrated vulnerable populations, limited healthcare access, and water/sanitation challenges. Mixed/all MGs types appeared in nine studies (33%).

The 28 included studies provided descriptive and evaluative data on EBS effectiveness. Among the 28 included studies: 75% of studies (n = 21) reported EBS systems as effective in detecting signals, generating early warnings, or meeting stated surveillance objectives. 11% of studies (n = 3) described intermediate effectiveness with some limitations identified. 14% of studies (n = 4) did not provide explicit effectiveness assessments or acknowledged gaps in evaluation frameworks.

Guidance documents and high-level technical reports do not usually evaluate specific EBS implementations in the same way as field reports. Thus, effectiveness was reported separately by document type. Among the 15 evaluative records (implementation reports or evaluation studies): 80% (n = 12) described EBS systems as effective in detecting signals or meeting surveillance objectives, 13% (n = 2) reported intermediate effectiveness with limitations, and 7% (n = 1) did not provide an explicit assessment.

For the integration pattern, most publications (64%, n = 18) integrated EBS with indicator-based and/or other surveillance types, while (36%, n = 10) applied standalone EBS approaches. Integrated surveillance is reported when EBS systems operate alongside indicator-based surveillance (IBS) systems, syndromic surveillance, and routine surveillance structures, with coordinated signal management and joint review processes. On the other hand, standalone EBS is also reported as an independent surveillance function focused on media monitoring, social media signals, and informal reporting channels without formal integration into national routine surveillance systems.

There are various scopes reported for EBS implementations, revealing gradual expansion from disease-specific to broader all-hazards surveillance. Half (50%) of studies (n = 14) specifically targeted infectious diseases including vector-borne diseases, respiratory infections, foodborne illnesses, and pandemic threats while 39% of studies (n = 11) explicitly described all-hazards surveillance encompassing infectious diseases, non-communicable diseases, injuries, environmental hazards, heat-related illnesses, accidents, and emergencies. On the other hand, 11% of studies (n = 3) focused on specific threat areas including bioterrorism (study 3, Tokyo Olympics) and special disease concerns (study 13), prioritized disease surveillance at EU level for Olympics.

The 28 included studies described diverse technological approaches to use while implementing EBS, ranging from manual systems to advanced artificial intelligence-enabled platforms. EIOS (Epidemic Intelligence from Open Sources) developed by WHO is featured in studies 3, 4, 6, 10. This platform performs automated media scanning from diverse pools of news agencies with the focus of for public health threats related news. EIOS was increasingly integrated into mass gathering EBS with human expert validation required for signal assessment, triage, verification, risk assessment and response. MedISys Platform is a European Commission-developed tool and is featured in studies 7, 11, 23 for automated media monitoring and multilingual signal detection from official and unofficial sources which is very similar to EIOS.

Hazard Detection and Risk Assessment System is featured in study 19 as a platform for monitoring news media, social media, and blogs for public health threats, used during European cultural events. A Caribbean-specific mass gathering surveillance platform is featured in study 2 as another platform integrating electronic data collection forms, tablet-based field entry, alert notification mechanisms, and real-time reporting features.

ESSENCE and OpenESSENCE: Featured in study 16. Syndromic surveillance systems with modular deployment, shareable visualizations, automated queries, and cohort tracking capabilities. While Twitter and Bing Query Logs which are featured in study 18 are internet-based syndromic surveillance using statistical modeling for mass gathering surveillance during festivals and Hajj.

Participatory Surveillance Applications are also featured in study 17 including mobile application (Healthy Cup app, later Guardians of Health) enabling direct public reporting of health symptoms during FIFA World Cup 2014, generating 47,879 participatory surveillance posts.

The review identified seven recurring challenges that hinder the implementation of Event-Based Surveillance (EBS) during mass gatherings:

The review identified five thematic recommendations to strengthen Event-Based Surveillance (EBS) in mass gathering settings:

Geographical patterns of the included studies show broad gap as 11 (39%, n = 11) studies come from just three countries (Saudi Arabia, Iraq, and the UK) while there is a significant underrepresentation of documented EBS experiences from: (1) countries in sub-Saharan Africa despite the frequent occurrence of major religious and cultural events; (2) Southeast Asia beyond Japan; (3) the Americas beyond Brazil and Caribbean region; and (4) lower-income and lower-middle-income countries. This highlights a geographic gap in the literature and underscores the need for broader global documentation efforts of EBS experiences during mass gatherings (1, 34).

Most documented events were either sporting events or religious ones which probably reflects the higher public, political and media visibility of such international gatherings compared to other types of events such as cultural festivals or refugee camps.

Sports events attract large numbers of participants and create sustained transmission opportunities over the event period. Religious events on the other hand, represent the second most frequently documented event type, featured in six studies encompassing some of the world’s largest gatherings by attendance. Religious events require unique surveillance efforts due to (1) extended duration; (2) geographically dispersed participants across multiple sites; (3) populations including older adults and immunocompromised individuals; (4) varied access to healthcare; and (5) cross-border pilgrimage patterns.

Cultural events’ underrepresentation in literature may reflect lower epidemiological priority perception compared to sportive and religious events, though they merit greater surveillance attention given growing event scale and international attendance.

While all-hazards approaches are increasingly adopted, infectious disease main focus remains dominant, suggesting that EBS frameworks have not fully integrated all public health threats comprehensively across all settings.

On the other hand, integrated disease surveillance approach reflects a growing recognition that EBS functions most effectively as component of existing comprehensive surveillance systems rather than an isolated function.

The most frequently mentioned best practice was multisectoral and stakeholders’ collaboration for EBS surveillance reflecting the multidirectional support needed for early detection, communication, validation and eventually response to detected signals. This is similar to existing literature focusing on the importance of multisectoral stakeholders in EBS (34, 35). Simultaneously, it was also found to be a main challenge in many studies showing the great importance of collaboration efforts in EBS activities during mass gatherings.

The second most important aspect was technology integration as proper technology integration was mentioned as a best practice while poor technology integration was highlighted as a main challenge in seven studies each. This aligns with other studies and reviews (36, 37) which is expected to increase due to recent Artificial Intelligence technologies and the limited human resources which makes high technology integration an important aspect for EBS specially that EBS includes media and social media which are heavily connected with such technology. Real time detection and communication was highlighted in accordance with existing literature (38) and high technology integration helps minimizing the lag time needed for detection, assessment and reporting any signal.

These findings underscore the complexity of implementing EBS during mass gatherings and indicates the urgent need for improvements in stakeholders’ coordination, better data automation and proper data management to enhance public health surveillance efforts.

The recommendations synthesized in this review primarily reflect actions proposed within the included records, focusing on how EBS in mass gatherings could be strengthened in practice.

According to this review findings, proper EBS integration with other types of surveillance is the best way forward to increase the effectiveness of EBS and to minimize the effort and resources needed for it as it will be a routine task in the national systems. This is agreed upon by other studies as a key recommendation (39, 40).

Risk based approaches and multisectoral collaboration are very crucial for EBS activities along with continuous evaluation of the system (34, 35, 41, 42).

Deeper analysis to the common areas reveals five key common themes consistently emerged across best practices, challenges and recommendations indicating common priorities for strengthening EBS during MGs according to the included publications. Surveillance systems integration and data quality improvement was the most frequently cited theme highlighted. Technology and infrastructure followed highlighting the potential of maximizing digital tools and Artificial Intelligence (AI) in EBS activities. Cross-sectoral collaboration was also highlighted which shows its significance particularly in cross-border and multisectoral contexts which is very common in mass gatherings. Early detection and real-time analysis and capacity building were each identified in the selected studies emphasizing the value of timely signal capture which is the main objective of EBS and the sustained support to national systems performing EBS activities.

These recommendations provide a roadmap for institutionalizing, upscaling and sustaining EBS activities in the context of mass gatherings with a strong emphasis on risk based and cross-sectoral approaches, evaluation and integration of EBS systems, technological advancement and knowledge sharing.

We recommend based on our findings that vigorous future research is essential for comparative studies and evaluation of current EBS systems during mass gatherings in a standardized way to document legacy and provide evidence-based guidance for global EBS during mass gatherings.

The main limitation in this scoping review is that it included only open-access, English-language sources which accordingly excluded relevant non-English or paywalled studies. The second limitation is that the search was limited to three databases and two gray literature sources, omitting other possible sources such as national Ministry of Health publications. Documentation bias might also add to these limitations due to lack of documentation of EBS even if it is already in place.