A rapidly spreading species of mosquito, Anopheles stephensi, is driving a surge in malaria cases across East Africa, threatening to unravel decades of progress against the disease. Experts warn that this urban-dwelling mosquito could dramatically increase malaria cases across the continent, already home to 95% of global cases and deaths.
A New Threat in the Fight Against Malaria
Anopheles stephensi, native to South Asia and the Middle East, was first identified in Africa in Djibouti in 2012. The tiny Horn of Africa nation had nearly eradicated malaria but saw a resurgence after the arrival of this mosquito, with cases exceeding 70,000 by 2020.
The species has since spread into Ethiopia, contributing to a dramatic rise in malaria infections. Ethiopia reported 7.3 million cases and over 1,150 deaths between January and October 2024, up from 4.1 million cases the previous year, according to the World Health Organization (WHO).
Unlike other malaria vectors, stephensi thrives year-round in urban settings, breeding in man-made water storage containers, gutters, and even air conditioning units. Its ability to resist traditional insecticides and bite earlier in the evening renders bed nets—once a cornerstone of malaria prevention—far less effective.
“The invasion and spread of Anopheles stephensi has the potential to change the malaria landscape in Africa and reverse decades of progress,” said Meera Venkatesan, malaria division chief for USAID.
Urbanization Fuels Spread
The spread of stephensi could prove catastrophic for Africa’s urban centers, with a 2020 study estimating that up to 126 million city dwellers across the continent could be at risk. Cities like Kenya’s coastal hub of Mombasa and Sudan’s Khartoum are particularly vulnerable due to dense populations and ample breeding grounds for the mosquito.
Egypt, which WHO declared malaria-free last month after a century-long battle, could also see its status threatened by the mosquito’s arrival.
The mosquito’s spread has remained limited to certain regions, such as Kenya’s hot and dry lowlands, without yet reaching higher-altitude areas like Nairobi. However, much about its biology and behavior remains unclear.
“Possibly it is climate-driven and requires high temperatures, but much more research is needed,” said Charles Mbogo, president of the Pan-African Mosquito Control Association.
Compounding Challenges
The emergence of stephensi comes amid growing concerns over other malaria-related challenges. Increasing drug resistance has been documented in Uganda, Rwanda, Tanzania, and Eritrea, raising fears that ineffective treatments could exacerbate the crisis.
“The arrival of resistance is imminent,” warned Dorothy Achu, WHO’s head of tropical and vector-borne diseases in Africa.
A new malaria parasite variant is also evading diagnostic tests, further complicating efforts to manage the disease.
“The increased transmission driven by stephensi could accelerate the spread of drug resistance or mutations in the parasite that make it harder to detect,” Venkatesan said.
Gaps in Coordination and Funding
Efforts to combat the mosquito’s spread have been hindered by fragmented responses and insufficient resources. While WHO is pushing for a coordinated continental strategy, scientists like Mbogo are calling for greater political will and cross-border collaboration.
“We share information as scientists with colleagues in neighboring countries,” Mbogo said. “But we need higher-level coordination. Cross-border data sharing and joint action are essential.”
Funding is also a significant barrier. Mbogo emphasized the need for increased investment in mosquito surveillance, public education, and preventive measures such as covering water storage containers.
The Way Forward
With Africa accounting for the majority of malaria cases and deaths globally, the emergence of Anopheles stephensi is a stark reminder of the challenges in eradicating the disease. While new tools, including vaccines, offer hope, experts stress that innovative solutions and international cooperation are urgently needed to prevent further setbacks.
As Venkatesan put it, “The stakes couldn’t be higher. We must act swiftly to protect decades of hard-won progress in the fight against malaria.”
