The influence of occupant behaviour on indoor air quality and COVID-19 risk in refugee shelters and temporary houses

There are growing concerns about poor indoor air quality in refugee shelters, particularly regarding chronic health conditions and the spread of airborne diseases like COVID-19. These issues are influenced by shelter design and occupants’ behaviours, such as cooking and window usage. However, behavioural aspects are often overlooked in shelter design due to the challenges of monitoring occupants, which can be costly and intrusive. To address this, we developed a cost-effective method for assessing shelters that combines self-assessed behavioural data, predicted ventilation rates, and a mathematical model for airborne disease transmission. This approach was tested in temporary housing following the 2020 floods in Kumamoto Prefecture, Japan. Results indicated that indoor CO2 levels exceeded national thresholds over 70% of the time, suggesting inadequate ventilation to mitigate airborne disease transmission. We estimated a 60–80% risk of COVID-19 transmission under these conditions. Our findings highlight severe health inequalities in forcibly displaced populations and provide: (i) the first comprehensive guide to monitoring indoor conditions and behaviours in these settings; (ii) a new model for assessing airborne disease risk. While the study focuses on COVID-19, the results can be extended to other airborne respiratory diseases through our reproductive number (R0) estimates.