The spread of a insecticide-immune mosquito that thrives in urban areas in East Africa is leading to a surge in malaria that could reverse decades of progress against the disease, experts say.

Africa accounts for approximately 95 percent of this population. 249 million malaria According to the latest data from the World Health Organization (WHO), 80 percent of deaths in the region were caused by children under the age of five.

But the emergence of an invasive mosquito species on the continent could greatly increase these numbers.

Anopheles stephensi is native to parts of South Asia and the Middle East, but was first spotted in the small Horn of Africa state of Djibouti in 2012.

Djibouti had almost eliminated malaria, but saw it make a slow but steady return in subsequent years, reaching more than 70,000 cases in 2020.

Later Stephensi came to neighboring Ethiopia and WHO says this is key to a solution There has been an “unprecedented increase” from 4.1 million malaria cases and 527 deaths last year to 7.3 million cases and 1,157 deaths between January 1 and October 20, 2024.

Unlike other species that are seasonal and prefer rural areas, stephensi thrives in urban environments year-round, breeding in man-made water storage tanks, roof gutters, and even air conditioning units.

It appears to be more resistant to insecticides and early evening bites than other hosts. This means that bed nets, until now the most important weapon against malaria, may be much less effective.

“The invasion and spread of Anopheles stephensi has the potential to change the malaria landscape in Africa and reverse decades of progress we have made towards malaria control,” Meera Venkatesan, head of USAID’s malaria division, told AFP.

‘More research is needed’

The fear is that stephensi will invade busy cities such as Mombasa on Kenya’s Indian Ocean coast and Sudan’s capital Khartoum, with a 2020 study warning it could reach 126 million city dwellers across Africa.

Just last month, after a century-long fight against the disease, the WHO declared Egypt malaria-free; this was a situation that could be threatened by the arrival of Stephensi.

But much is unknown.

Stephensi is confirmed to be in Kenya in late 2022, but has so far remained in warmer, drier regions without reaching the high-altitude capital Nairobi.

“We don’t yet fully understand the biology and behavior of this mosquito,” Charles Mbogo, president of the Pan-African Mosquito Control Association, told AFP.

“It’s probably climate driven and requires high temperatures, but much more research is needed.”

He called for increased funding for trapping and testing mosquitoes and educating the public on preventative measures such as covering water containers.

Proliferation of threats

The spread of Stephensi may coincide with other worrying trends, including increasing evidence of drug-resistant malaria recorded in Uganda, Rwanda, Tanzania and Eritrea.

“The coming of the resistance is near” said Dorothy AchuWHO’s head of tropical and vector-borne diseases in Africa.

He said WHO was working with countries to diversify treatment programs to delay resistance.

A new variant of malaria is also evading tests used to diagnose the disease.

“Increased transmission by Stephensi could potentially help accelerate the spread of other threats, such as drug resistance or another mutation in the parasite, making it less detectable with our most widely used diagnostic methods,” said USAID’s Venkatesan.

Another added challenge is the lack of coordination between African governments.

Achu said the WHO was working on “a more continental approach.”

But Mbogo in Kenya said “more political will” was needed.

“As scientists, we share knowledge with our colleagues in neighboring countries,” he said. “But we need to reach a higher level. We need cross-border collaborations, data sharing.”