From the "Madding Crowd" to mass gatherings-religion, sport, culture and public health.

Human behavior has long engaged in collective behavior assembling in crowds. The Christian pilgrimage to the Holy Land has been recorded since the 4th century, while the Hajj, Islam's great pilgrimage, has existed for fourteen centuries, of which a body of literature devoted to the travelogues of the Hajj has been recorded for over ten centuries. Football is a sport played worldwide by more than 1.5 million teams and in 300,000 clubs. Most however play outside of the officially organized sphere: more than 4 percent of the global population plays football, including 270 million amateur players. Assembling for specific events is a uniquely human behavior, though the formal study of crowds did not begin until the mid-Twentieth Century. Today Mass Gathering Medicine focuses on the public health challenges to hosting events attended by a large enough number of people, at a specific site, for a defined period of time, likely to strain both the planning and response to the mass gathering of a community, state, or nation. All of us can recall attending a mass gathering, whether it be watching one's favorite rock group in performance or assembling for religious pilgrimage. Certainly, the event itself is transporting and transforming and the unison of behaviors and activities can be enormously enriching, uplifting and overwhelming, just as much as they may be at times dangerous and high risk. This review seeks to draw contrasts and comparisons between sporting gatherings and religious gatherings with a chief focus on Hajj, among the largest of all mass gatherings today. We will find there are some powerful similarities as well as stark differences. Each bequeaths a legacy which can inform the other and, as we make our observations, we join with you and the legions of other investigators who continue to remain fascinated and enthralled by mass gatherings which are among the most beloved and beholden events of modern humanity.