Table 3.

Characteristics of the included studies in the review (N=8).

Study, year	Study type	Study objective	Gathering type	Event location and duration	Number of attendees	Attendees’ characteristics
Aggrawal et al [24], 2020	Descriptive	To describe the public health preparedness and implementation of on-site disease surveillance during the Prayagraj Kumbh	Religious	The Prayagraj Kumbh, India January 14, 2019, to March 4, 2019	120 million	Pilgrims Semipermanent residents (comprising sages and pilgrims following different Hindu sects known as akhara sadhus and kalpawasis) who resided at the MGa site for 3 months Traveling pilgrims came for a period of 2-3 days to take a dip in the holy river
Bieh et al [27], 2020	Descriptive analysis	Describe the early warning findings at the Hajj to highlight the pattern of health risks and the potential benefits of the disease surveillance system	Religious	The Hajj Mekkah, Saudi Arabia August 9, 2019, to August 14, 2019	2,489,406 pilgrims 75% international pilgrims	55.6% male attendees 9.2% Saudi nationals
Alotaibi et al [25], 2017	Descriptive	Describe the characteristics of the IDSSb during the 2015 Hajj; highlight best practices and gaps and propose strategies for strengthening and improvement	Religious	The Hajj Mekkah, Saudi Arabia Dhu-AlHijjah 8-14, 2015	1,952,817 pilgrims 193,645 Saudi and 759,172 non-Saudi individuals	Domestic Saudi and non-Saudi pilgrims from 135 countries
Leal Neto et al [21], 2017	Descriptive	Describe the use of a participatory surveillance app for early detection of acute disease outbreaks during the FIFAc World Cup	Sporting	FIFA World Cup, Brazil May 12, 2014, to July 14, 2014	N/Ad	N/A
White et al [29], 2018	Descriptive	Describe the enhanced surveillance system implemented by Pohnpei State and discuss the sustainable benefits of surveillance of MGs	Sporting	Micronesian Games The Pohnpei Federated State of Micronesia July 19, 2014, to July 29, 2014	1700	Athletes and officials
Hoy et al [30], 2016	Descriptive analysis	Report the experience of providing SSe for the FOPAf	Cultural festival	FOPA, Honiara, Solomon Islands July 1, 2012, to July 14, 2012	<3000	Artists and performers
Nsoesie et al [31], 2015	Descriptive	Review and describe novel approaches to disease surveillance	Religious and sporting	The Hajj Kumbh Mela Olympic Games Athletics Super Bowl	N/A	N/A
Severi et al [28], 2014	Descriptive and evaluative	Describe the EBSg implemented by the health protection agency for the London 2012 Olympic and Paralympic Games Evaluate the system’s attributes to identify lessons and contribute knowledge and evidence for planning future MG events	Sporting	London Olympic and Paralympic Games London, United Kingdom July 2, 2012, to September 23, 2012	15,000 athletes, 70,000 volunteers, and 10 million tickets in 11 UK cities	Athletes and volunteers

^aMG: mass gathering.

^bIDSS: infectious disease surveillance system.

^cFIFA: Federation International Football Association.

^dN/A: not applicable.

^eSS: syndromic surveillance.

^fFOPA: Festival of Pacific Arts.

^gEBS: event-based surveillance.