Anopheles stephensi is invading African cities where populations have no malaria immunity

Anopheles stephensi, an urban-adapted malaria vector from South Asia, has colonized at least 9 African countries since its first detection in Djibouti in 2012 and is spreading uncontrollably. Unlike native African vectors, An. stephensi thrives in man-made water containers (cisterns, construction sites, discarded tires) found abundantly in cities, and it feeds on both humans and animals while resting both indoors and outdoors. This creates a novel and devastating threat because urban populations in Africa have historically had low malaria exposure and therefore lack acquired immunity. When transmission spikes in these immunologically naive urban populations, severe disease and death rates are disproportionately high. In Djibouti, malaria cases surged from fewer than 1,000 per year to over 20,000 following the stephensi invasion. Models suggest An. stephensi could increase P. falciparum cases by 50% continent-wide without intervention. The problem persists because existing vector control tools (LLINs, IRS) were designed for rural endophilic vectors, not an urban species that breeds in artificial containers and rests outdoors. Larval source management in sprawling, unplanned urban environments with thousands of potential breeding sites is operationally overwhelming. Critically, there is no international coordination mechanism or funding stream specifically targeting invasive vector species.