Public health preparedness and infectious disease risk management across religious mass gatherings: a comparative analysis of Hajj, Umrah, Arba’een and Kumbh Mela

BACKGROUND: Religious mass gatherings (MGs) such as Hajj, Umrah, Arba'een and Kumbh Mela attract tens to hundreds of millions of participants annually, posing unique challenges for infectious disease control, surveillance and health system preparedness. METHODS: We conducted a structured comparative analysis of these four MGs, evaluating attendance scale, participant demographics, governance structures, epidemiological risks and public health response strategies. Data were synthesized from international public health reports, peer-reviewed literature and national MG health policies. RESULTS: Hajj attracts 1.8-3 million pilgrims annually from > 180 countries, while Umrah draws ~ 30 million yearly with similar global diversity. Arba'een hosts 20-22 million participants mainly from Iraq, Iran and neighbouring nations. Kumbh Mela peaks at tens of millions overall, exceeding 50 million on high days, predominantly Indian nationals plus international visitors. Common threats across these mass gatherings include respiratory pathogens, water- and food-borne illnesses and vaccine-preventable diseases, amplified by crowding and diverse origins. Successful public health responses emphasize pre-event vaccination (e.g. meningococcal ACWY for Saudi MGs), real-time surveillance systems and multisectoral coordination among stakeholders. CONCLUSIONS: Comparable yet distinct, these MGs require tailored risk-based frameworks emphasizing leadership, surveillance, prevention and surge capacity. Our analysis proposes a unified model to strengthen global MG policies and practices, enhancing health security for future events.