Aerial shot of the Kibera slum, Africa’s largest slum in the heart of Nairobi, Kenya. Ben Schusterbauer
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A systematic review in Climate warns that extreme heat is deepening urban inequality across Africa, hitting informal settlements hardest.
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Drawing on 21 studies from 2010–2024, it links heat to direct illnesses like dehydration, stroke and respiratory problems, and indirect impacts such as depression, infectious disease and child mortality, driven by poor housing, overcrowding and weak infrastructure.
A new study published in the journal Climate on August 17, 2026, reveals that extreme heat poses significant health risks to residents of Africa’s informal settlements, exacerbating existing inequalities.
The findings show that heat is not simply an environmental challenge but an urban inequality crisis, with disadvantaged communities facing greater risks because of poor housing, limited water access, inadequate infrastructure, and weak healthcare services.
Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, the researchers searched 11 academic databases and considered peer-reviewed studies published from 2010 to 2024 in English, French or Portuguese. After screening 96,608 records, only 21 studies met the final inclusion criteria.
Seven studies were conducted in South Africa, six in Kenya, four in Tanzania, and one each in Cameroon, Egypt, Nigeria, and Ghana. Seventeen studies examined heat-related illness, while four investigated mortality.
Among the 17 studies investigating the effects of heat on morbidity, seven assessed both direct and indirect effects, while ten focused exclusively on direct heat-related effects.
The evidence demonstrates that extreme heat affects health through both direct and indirect pathways and are strongly influenced by adverse environmental conditions, vulnerable livelihoods, inadequate housing, socioeconomic disadvantage, and limited adaptive capacity.
Direct health effects of heat
The direct health effects of heat indicate that populations residing in disadvantaged urban areas experience substantial health impacts attributable to heat exposure. In Dar es Salaam, Tanzania, residents frequently reported skin rashes, headaches, discomfort, sleep disturbances, muscle cramps, and fatigue during periods of extreme heat. In Nairobi, Kenya, heat-related symptoms included fever, excessive sweating, influenza-like illness, cough, stress, anxiety, and stroke. In South Africa, dehydration, heat exhaustion, and heatstroke were among the most commonly reported conditions. Fainting, dizziness, and irritability were additionally documented across multiple settings. A qualitative study conducted in Cairo, Egypt, among 85 women found that pregnant women and children were especially susceptible to physical discomfort and respiratory symptoms such as cough.
Indirect health effects of heat
Heat can also worsen existing health conditions and contribute to indirect health problems. Studies in Accra, Ghana, linked heat exposure with depression, infectious diseases such as malaria and cholera, and cardiovascular and respiratory illnesses. In Nairobi, Kenya heat was found to aggravate conditions including diarrhoea, HIV, hypertension, pneumonia, and malnutrition. Evidence from KwaZulu-Natal, South Africa identified tuberculosis and diabetes as additional heat-exacerbated conditions, with children representing the most vulnerable group. In Dar es Salaam, Tanzania, heat exposure was further associated with poor mental health outcomes and reproductive health problems.
Mortality associated with heat exposure
The relationship between heat and mortality was more complex. Some research in Nairobi linked temperatures above local heat thresholds with child mortality and deaths from non-communicable diseases. However, studies in South Africa found that cold-related excess mortality was greater than heat-related mortality, partly because cold days were substantially more frequent than hot days during the study periods.
Vulnerability factors to heat-related health effects
The study shows that vulnerability to extreme heat is multidimensional. Poor housing, overcrowding, inadequate ventilation, limited water, poverty, insecure employment, and insufficient public infrastructure can intensify exposure and reduce residents’ ability to adapt.
Overall, the findings demonstrate that extreme heat represents an important and unequal health threat in African informal settlements. Effective adaptation therefore requires approaches that address both heat exposure and the underlying socioeconomic and environmental conditions that increase vulnerability.
