Heat-related illness at mass gatherings, such as major sporting, religious and cultural events, has become a significant public health and operational risk, affecting spectators, attendees, volunteers and workers. The World Health Organization (WHO) has today published a new review of evidence with guidance showing that most of the heat-related illnesses at major events can be prevented or treated on site when timely risk management measures are put in place.
The evidence review, covering studies published between 1980 and 2025, documented nearly half a million medical encounters at mass gatherings, including more than 22 000 heat-related illnesses. However, studies also showed that when on-site medical systems are well organized, more than 90% of patients can be treated at event venues, substantially reducing demand on local hospitals and ambulance services.
"Extreme heat is an increasing threat to health, safety and operational continuity in mass gatherings, and must be addressed not only as an environmental hazard but as a core operational and governance challenge," said Dr Chikwe Ihekweazu, Executive Director, WHO Health Emergencies Programme. "Protection cannot rely on individual behaviour alone; by strengthening consistent risk assessment, preparedness and response, we can reduce immediate harm and support safer, more resilient event planning in a warming world."
There has been an estimated 63% increase in heat-related deaths since the 1990s, with an average of 546 000 deaths occurring annually between 2012 and 2021. Mass gatherings can amplify heat risks in several ways. Long periods outdoors with exposure to heat and sun, dense crowds, limited access to safe water, travel-related stress, unfamiliarity with local climatic conditions, and competing demands on health services can combine to create dangerous conditions.
According to the Intergovernmental Panel on Climate Change (IPCC), hot extremes, including heatwaves, have become more frequent and more intense across most land regions since the 1950s, mainly as a result of climate change. Further increases in the frequency and intensity of hot extremes are projected with every additional increment of global warming.
To help host countries and event organizers better anticipate and manage heat-related health risks, WHO is releasing a new set of resources under the title Prevention and management of heat-related illness at mass gatherings, building on evidence synthesized through systematic reviews and lessons learned from mass gathering events worldwide.
The findings reinforce the importance of investing in preparedness and response measures before temperatures reach dangerous levels. The most effective approaches combine multiple measures, including:
- accessible and safe drinking water and toilets;
- cooling infrastructure;
- schedule adjustments;
- crowd-flow management;
- workforce protection measures;
- public communication;
- real-time surveillance; and
- well-prepared on-site medical services.
The guidance focuses on spectators, attendees, volunteers and workers. It is intended to complement WHO's guidance on heat-health action plans as well as existing national heat-health action plans, occupational health and safety requirements, emergency preparedness arrangements and clinical guidance.
The guidance emphasizes a whole-of-event approach, recognizing that factors such as venue design, crowd management, water and sanitation, transport, security, communications and workforce management all influence access to cooling, safe water and timely medical care. It covers the full event cycle and should be integrated into broader emergency preparedness and all-hazards risk management. WHO is calling on governments, event organizers and partners to integrate heat risk management into health planning, preparedness and operations for mass gatherings worldwide.
About WHO
Dedicated to the well-being of all people and guided by science, WHO leads and champions global efforts to give everyone, everywhere, an equal chance at a safe and healthy life. We are the United Nations' agency for health that connects nations, partners and people in more than 150 locations – leading the world's response to health emergencies, preventing disease, addressing the root causes of health issues and expanding access to medicines and health care. Our mission is to support all countries to promote, provide and protect health. "Together for health. Stand with science", the theme of World Health Day 2026, marks a year-long campaign to highlight science as the foundation for protecting health and well-being worldwide.
