Future Explained

Will a New Mosquito Bring Malaria Back to Cities That Don't Have It Today?

Anopheles stephensi breeds in water tanks and construction sites, not rural pools, and has already spread to 14 African countries. A 2025 climate model projects it could reach 57 by 2100, including 12 currently malaria-free countries.

Anopheles stephensi, the mosquito spreading into African cities. CDC/James Gathany, public domain.

Malaria in Africa has always been a rural disease, spread by mosquitoes that breed in puddles, rice paddies and riverbanks far from city centres. Decades of bed nets, indoor spraying and rural clinic access were built around that pattern, and they have driven most of the continent's progress against the disease. Anopheles stephensi does not follow the pattern at all. Native to South Asia and the Arabian Peninsula, it breeds happily in water tanks, barrels, tyres and construction sites, the standing water found in every growing African city rather than the countryside. Since arriving on the continent, it has established itself in 14 countries and reached urban areas of Djibouti, Ethiopia and Sudan, environments where malaria control was never designed to operate, and where the disease had often been rare or absent for years.

How far could this mosquito actually spread?

Further than its current footprint suggests. Professor Maria Anice Sallum at the University of Sao Paulo led a July 2025 study modelling the insect's future climate suitability out to 2100, using three global climate models and eight forecasting algorithms. Today, the mosquito can already survive in areas covering roughly 13% of the planet's dry land, home to about 40% of the world's population. Sallum's team projects that could grow to more than 30% of dry land and 56% of the global population by the end of the century. In Africa alone, the study finds 57 countries could become climatically suitable, including 12 that currently have no malaria transmission at all. The same modelling exercise found expansion likely well beyond Africa too, into parts of Brazil, Mexico and Bolivia, and further into the Mediterranean coasts of Spain, Portugal and Greece, though the African cases matter most here because they include countries that eliminated malaria only in the last generation.

Does climate suitability mean malaria will actually spread?

The authors are careful not to overclaim it. Sallum and her co-authors describe their maps as showing "potential zones of vector-parasite compatibility, rather than deterministic maps of disease expansion." A city can be climatically suitable for the mosquito without automatically getting malaria: that also depends on whether the specific Plasmodium parasites that cause the disease can develop inside local mosquito populations, how humid the air is, how many people live close to breeding sites, and how strong the local health system is. The study's own conclusion is that future work linking parasite biology to these climate maps is still needed before anyone can turn a suitability map into a real risk forecast.

What does the spread actually mean for people living in cities today?

Researchers at Belgium's Institute of Tropical Medicine, who have studied the mosquito's arrival in the Horn of Africa directly, put a number on the near-term stake: up to 126 million additional people are potentially at risk of malaria in African urban environments because of it. That figure describes people newly exposed by the mosquito's urban habits, not a prediction that all of them will be infected. "It is vital that multi-sectoral vector control strategies are designed and tested, tailored to the new urban context," said Fatou Jaiteh, a researcher in the institute's socio-ecological health unit. Her colleague Professor Koen Peeters called it "a complex problem" that "requires a complex socio-ecological approach," pointing to construction workers, migrants and other mobile populations who move between the mosquito's breeding sites and rarely feature in traditional rural malaria campaigns. Dr Anne Wilson, co-director of the institute's CEASE project studying the mosquito's ecology, is part of the same push to understand how an urban vector behaves differently from a rural one before control strategies are designed around it.

What is actually being tried against it?

Standard African malaria control was not built for this mosquito. Researchers are now designing responses specifically for it. A team led by Gabrielle Hunter at Johns Hopkins University's Center for Communication Programs, writing in Malaria Journal, has proposed early-awareness campaigns launched before the mosquito establishes itself in a new city, tailored outreach to construction workers and other high-mobility groups, community partnerships built on trust rather than top-down instruction, practical guidance on managing water containers, and local hiring and training for larvicide application rather than external teams parachuting in. None of these approaches has been tested at the scale the climate projections describe, and each depends on health systems built for rural malaria control noticing a different mosquito in a different place before it spreads further. Cities in the Horn of Africa are testing right now whether they can get ahead of a mosquito that keeps finding new water tanks to breed in, instead of reacting after it has already arrived.

Institutions in this article: Universidade de Sao Paulo, Brazil; Institute of Tropical Medicine, Antwerp; Johns Hopkins Center for Communication Programs.

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