FOR YEARS, global public-health officials have been at war with malaria, a disease that kills more than 445,000 people annually, about 70 percent of them children under 5 years old. The number of cases and deaths has steadily dropped for a decade and a half. As philanthropist Bill Gates told a global conference in April, half the world is now malaria-free. But the battle shows signs of stalling.

In 2016, the latest year for which data has been published, the number of malaria cases went up to 215 million, from 210 million the year before. The director general of the World Health Organization, Tedros Adhanom Ghebreyesus, said, “We are beginning to see reversals in the gains achieved.” Africa still accounts for 90 percent of the burden, but Venezuela, once nearly malaria-free, shows that when a nation falls apart, disease can rush in. A WHO official has reported that the incidence of malaria in Venezuela in 2017 jumped 69 percent from the previous year, to more than 400,000 cases, and is five times higher than in 2013. As Venezuela fell into political and economic chaos, its public-health systems collapsed, leaving the country without insecticides, drugs, mosquito nets, diagnostic equipment and surveillance, all key tools in the battle against the disease, caused by a parasite and spread by the mosquito.

As Mr. Gates pointed out, globally, tools that brought progress are wearing out. The nets, sprays and drugs “aren’t working as well as they used to.” The mosquitoes are increasingly resistant to the insecticide widely used in mosquito nets, pyrethroid. At the same time, in the Mekong River region in Southeast Asia, a commonly used anti-malaria drug, artemisinin, has been losing its punch as the parasites become resistant. So far, this resistance has not spread to Africa, fortunately. But there has been a sharp drop-off of indoor spraying in Africa, and only slightly more than half of all people in sub-Saharan Africa are sleeping under treated nets, the primary prevention method. It is critical in malaria cases to get prompt health care, but still only 1 in 3 children in Africa do so. The WHO chief said the $2.7 billion committed annually to anti-malaria efforts is less than half of what is needed.

For the first time, a vaccine shows partial protection against malaria in young children and has been cleared for pilot introduction in Africa to complement other efforts. Over the longer run, there is hope that technology such as the genetic editing tool known as CRISPR can be used to modify mosquitoes so they don’t spread the disease. This seems like an example of the kind of genetic editing that would present a handsome payoff to humankind and be worth the risk if it works.

The fight against malaria can’t be won with a dramatic “moonshot” campaign but rather by action on many fronts. A stall, after so much promise, would be terrible and costly.

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