As part of the effort, donors are funding the distribution of mosquito nets and training health workers.

Image An informational flier on malaria, distributed at Vietnamese pharmacies. A drug-resistant strain of the disease has been detected in the country. Credit... Quinn Ryan Mattingly for The New York Times

“If this gets to Africa, it’s going to be catastrophic,” Dr. Christopher V. Plowe, a malaria expert at the University of Maryland School of Medicine, said in a Skype interview from Myanmar.

A key challenge, experts said, is that malaria is most intense in forests and jungles, and people living there are notoriously difficult to monitor. The problem is even worse where there is fighting, such as along Myanmar’s border with China.

Dr. Do Kim Giang, a Vietnamese medical official who has worked in Bu Gia Map District, said he saw no hope of eradicating malaria there. “We can only prevent cases from turning deadly,” he said during an interview at a no-frills health clinic in a neighboring district. Binh Phuoc Province, which includes Bu Gia Map, accounted for 39 percent of Vietnam’s 1,601 confirmed cases of falciparum malaria in the past year, according to W.H.O. data.

Experts are cautiously optimistic that the next “miracle cure” will be available soon.

The drug companies Sanofi and Novartis are each in the late phases of testing new combination therapies. At least one could win W.H.O. approval by 2022 or 2023, or even by 2020 if a drug-resistance crisis broke out in Africa, said Dr. Timothy N. Wells, chief scientific officer for the Medicines for Malaria Venture, a Swiss public-private partnership that coordinates most of the world’s malaria research. Several other drugs, none of them artemisinin-based, are in the pipeline, he said.

“Our portfolio of new molecules is pushing forward at what I’d consider a reasonable speed,” Dr. Wells said.