DOI: 10.12688/f1000research.188197.1 ISSN: 2046-1402

Heat-related illness during Hajj mass gatherings: a systematic review of burden, risk factors, surveillance approaches, and mitigation strategies

Hassan Zaher M Alqarni, Hazim Saeed Raffaa, Roqayya Mohammed Alhayyani Asiri, Nouf Abdulrahman S Alqahtani, Sultan Abdullah Albqami, Afnan Hezam S Alaklabi, Noha Megaad N Alghamdi, Norah Nasser A. Alshahrani, Hajar Mohammed S Alsaluli, Abdulaziz Mesheil M Alalyani, Norah Rajeh M Alaklabi, Jawaher Rajeh M Alaklabi, Jalal Mahfouz Hassan, Saad Aeydh A Alkarni
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Background Heat-related illness (HRI) is a major public health challenge during the Hajj pilgrimage, one of the world’s largest annual mass gatherings. This study systematically reviewed the burden, risk factors, surveillance approaches, and mitigation strategies related to HRI during Hajj. Methods This systematic review was conducted according to PRISMA 2020 guidelines. PubMed, Scopus, Web of Science, and Google Scholar were searched from inception to February 2026. Observational studies reporting heat-related outcomes among Hajj pilgrims were included. Data were extracted on HRI burden, risk factors, surveillance systems, and preventive measures. Study quality was assessed using the Newcastle–Ottawa Scale. Results Twelve studies conducted in Saudi Arabia were included. Heat exhaustion was the most commonly reported condition, accounting for up to 71.5% of cases, whereas heat stroke accounted for 28.5–29% and was associated with substantial mortality. Historical reports documented up to 1,012 heat stroke deaths during extreme heat seasons, with incidence rates reaching 251 per 100,000 pilgrims. Major risk factors included older age, comorbidities, lack of acclimatization, high ambient temperatures, crowding, dehydration, prolonged walking, and inadequate sun protection. A limited number of studies reported advanced surveillance approaches, including machine-learning-based diagnostic modeling, climate-linked predictive models, and implementation of the Health Early Warning System (HEWS). Cooling infrastructure, shaded pathways, and air-conditioned tents were associated with reductions in heat stroke incidence and mortality. Conclusion HRI remains a significant yet preventable threat during Hajj. Strengthening surveillance systems, climate-adaptive mitigation strategies, and targeted preventive interventions is essential to improve pilgrim safety.

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