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The narrow wooden benches in the student health clinic at Dire Dawa University in Ethiopia\u2019s second-largest city began to fill up in March last year: feverish students slumped against their friends, cradling aching heads in their hands.<\/p>\n
Helen Asaminew, the presiding nurse, was baffled. The students had the hallmark symptoms of malaria. But people didn\u2019t get malaria in cities, and the students hadn\u2019t traveled anywhere. It was the dry season. There was no malaria for hundreds of miles.<\/p>\n
Yet when Ms. Asaminew had their blood tested, the telltale ring-shaped parasite signaling malaria turned up in most of the samples. By April, one out of every two students living in the male dormitories had the disease, 1,300 cases in all.<\/p>\n
The crowded clinic was the starting point of a medical mystery that forewarns an alarming new public health crisis in Africa.<\/p>\n<\/div>\n<\/div>\n
At its center is Anopheles stephensi, a malaria-carrying species of mosquito that arrived in the port city of the tiny East African nation of Djibouti a decade ago and was largely ignored by public health officials. It is resistant to all insecticides and has adapted to thrive in urban environments and survive in dry seasons. It is now breeding in locations across the center of the continent, and entomologists say further spread is inevitable.<\/p>\n<\/div>\n<\/div>\n
Africa has expertise and strategies to fight malaria as a rural disease but now faces the threat of urban outbreaks, putting vastly more people at risk and threatening to wipe away recent progress against malaria, which still kills 620,000 people each year, mostly in Africa. Although some mosquito experts say it is too soon to be certain of the magnitude of the threat, the potential for outbreaks in cities, they fear, may set up a competition between urban and rural areas for scarce resources to fight the disease.<\/p>\n<\/div>\n<\/div>\n
Stephensi breeds in water and thrives in congested cities, where unreliable piped-water systems often force people to store water around their homes, and poor trash collection provides ample spots (such as old bottle caps) for mosquitoes to lay eggs. The species is poised to descend on what public health experts describe as a largely malaria-naive human population: Most urban dwellers don\u2019t have immunity from repeated prior exposure and may fall much sicker.<\/p>\n<\/div>\n<\/div>\n
\u201cIt\u2019s incredibly worrying: In places with stephensi <\/em>established, we see cases going through the roof,\u201d said Sarah Zohdy, who heads a task force on the invasive species for the U.S. President\u2019s Malaria Initiative, a United States government program that fights malaria worldwide.<\/p>\n Africa is the least-urban continent, but also the one with the fastest-expanding cities: 50 percent of its population is projected to live in cities by 2030. Since emerging in Djibouti and Ethiopia, stephensi has been found in Kenya and Sudan, where the capital cities, Nairobi and Khartoum, are each home to about six million people, and in Nigeria, where the city of Lagos has a population of 16 million, double that of New York.<\/p>\n Researchers led by a University of Oxford entomologist assessed Africa for suitable habitat for stephensi and concluded that the species\u2019s continued expansion puts an additional 126 million people<\/a> at risk of malaria.<\/p>\n<\/div>\n<\/div>\n