WHO Releases Guidance to Prevent Heat-related Illness at Mass Gatherings

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 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 Program. “Protection cannot rely on individual behavior 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.”

An estimated 63% increase in heat-related deaths have occurred 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, WHO said. 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 because of climate change. Further increases in the frequency and intensity of hot extremes are projected with every additional increment of global warming.

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.
• 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.