Mass gatherings: A one-stop opportunity to complement global disease surveillance

Emerging infections including those resulting from the bioterrorist use of infectious agents have indicated the need for global health surveillance. This paper reviews multiple surveillance opportunities presented by mass gatherings (MGs) that align with fundamental questions in epidemiology (why, what, who, where, when and how). Some MGs bring together large, diverse population groups coming from countries with high prevalence of communicable diseases and disparate surveillance capacities. MGs have the potential to exacerbate the transmission dynamics of infectious diseases due to various factors including the high population density and rigor of events, increase in number of people with underlying diseases that predisposes them to disease acquisition, mixing of people from countries or regions with and without efficient disease control efforts, and varying endemicity or existence of communicable diseases in home countries. MGs also have the potential to increase the opportunities for mechanical and even heat-related injuries, morbidity or deaths from accidents, alcohol use, deliberate terrorist attacks with biological agents and/or with explosives and from exacerbation of pre-existing conditions. Responding to these wider range of events may require the use of novel bio-surveillance systems designed to collect data from different sources including electronic and non-electronic medical records from emergency departments and hospitalisations, laboratories, medical examiners, emergency call centres, veterinary, food processors, drinking water systems and even other non-traditional sources such as over-the-counter drug sales and crowd photographs. Well-structured, interoperable real-time surveillance and reporting systems should be integral to MG planning. The increase in magnitude of participants exceeding millions and diversity of people attending MGs can be proactively used to conduct active surveillance of communicable and non-communicable diseases or indicators of global and national public health interest during MGs than can collectively complement efforts to enhance global health security.