An invasive mosquito species known as Anopheles stephensi, which carries malaria and resists common insecticides, is rapidly spreading across Africa, raising significant public health concerns. First detected on the continent a little over a decade ago in Djibouti, the species has expanded its range westward to Ghana and south through Kenya, demonstrating greater speed and adaptability than previously anticipated.

Unlike the native African malaria vectors, Anopheles stephensi thrives in urban environments and is less affected by seasonal dry spells. This poses a new challenge for malaria control, particularly in densely populated cities such as Lagos in Nigeria and Kinshasa in the Democratic Republic of the Congo, each harboring about 20 million residents. Public health experts warn that these urban populations, which generally lack immunity to malaria, could experience severe outbreaks, transmitted by a mosquito that sustains malaria transmission year-round rather than seasonally.

Genomic analyses of mosquito samples across ten African countries reveal that these mosquitoes carry genetic mutations conferring resistance to all insecticides currently used in spraying and control efforts throughout the continent. This resistance significantly reduces the effectiveness of existing malaria intervention strategies and complicates efforts to curb the spread.

Before Anopheles stephensi’s arrival in Djibouti around 2013, malaria cases were on the verge of elimination, with only 27 cases recorded in 2012. Within a year of the mosquito’s detection, cases surged to around 1,700 and escalated to over 70,000 by 2020. Similar patterns have been observed in Ethiopia’s Dire Dawa, where a sudden rise in malaria cases in 2022 was linked to the invasive mosquito.

Researchers indicate that the mosquito likely arrived via shipping routes from South Asia. After establishing itself in Djibouti, the population split into three main groups, dispersing into Ethiopia and Kenya, crossing into Yemen via the Red Sea, and moving westward across Sudan into West Africa. Recent findings reveal that Anopheles stephensi has been detected in Niger for the first time, marking another step in its westward expansion across the continent.

Efforts to monitor and respond to this threat are hampered by constrained resources, ongoing regional conflicts, and funding cuts in malaria control programs. For example, surveillance—which is critical for guiding interventions such as bed net distributions—has been one of the first casualties of budget reductions in high-burden countries. Health professionals report that these challenges are especially acute in conflict-affected areas such as Sudan and Yemen, where instability and limited infrastructure restrict vector surveillance and response capacity.

While the mosquito’s rapid adaptation and wide spread have alarmed experts, some also acknowledge the species’ remarkable ability to establish itself despite losing much of its initial genetic diversity—a characteristic uncommon among invasive species.

Scientists conducting genomic studies highlight the urgency of reallocating resources and developing new strategies to address this evolving threat. However, they caution that even comprehensive data will have limited impact without adequate infrastructure and funding to implement effective malaria control measures across affected regions.