Whilst we think of the home as a sanctuary, in Africa, around 80% of malaria bites occur indoors at night. Preventing mosquitoes from getting indoors is a simple way of protecting people from this often lethal disease.
In 2019, the World Health Organisation estimated that malaria killed 386,000 people in sub-Saharan Africa, mainly children. Meanwhile, there is growing evidence that house design can decrease the force of malaria infection.
As most mosquitoes fly low to the ground, a team of researchers led by Professor Steve Lindsay wondered whether if, by raising a house, malaria mosquitoes would struggle to find the occupants.
Mozzies decrease as heights increase
Using four experimental houses, the researchers found that the number of female malaria mosquitoes collected in the huts declined with increasing height, decreasing progressively as the hut’s floor moved further from the ground.
Huts with floors 3 metres above the ground had 84 % fewer mosquitoes than those on the ground. Interestingly, if this reduction correlates to a similar reduction in malaria transmission, it would be comparable to that of an insecticide-treated net that can reduce malaria transmission by 40-90 %.
Working with a team of architects and builders from the Royal Danish Academy – Architecture, Design and Conservation, the team constructed four experimental houses in The Gambia, each of which could be raised or lowered.The height of each house was changed weekly and, after analysing the results, they found that increasing the height of a hut progressively reduced the number of mosquitoes entering the hut.The reasons for this are twofold: First, malaria mosquitoes have evolved to find humans on the ground. Second, at higher heights, the carbon dioxide odour plumes coming out of the huts are rapidly dispersed by the wind, so mosquitoes find it more difficult to find a person to bite.
Building for the future
These findings have real-world implications for the growing population of sub-Saharan Africa whose population will more than double between 2019 and 2050, and the region will become the world’s most populated by 2062.Coincident with the increasing growth rate, there has been an unprecedented improvement in the housing stock in sub-Saharan Africa. With an additional 1.05 billion people by 2050, there has never been a better time to make houses healthier for people.
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This work was done in collaboration with the Medical Research Council’s Unit The Gambia at the London School of Hygiene and Tropical Medicine, the Royal Danish Academy – Architecture, Design and Conservation, Denmark and the London School of Hygiene and Tropical Medicine.