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."