Strains of drug-resistant malaria are becoming more dominant in Vietnam, Laos and northern Thailand after spreading rapidly from Cambodia.
Malaria is caused by parasites which are carried by mosquitoes and spread through their blood-sucking bites. Malaria can be successfully treated with medicines if it is caught early enough, but resistance to anti-malarial drugs is growing in many parts of the world, especially in south east Asia.
Scientists have discovered a growing number of cases where the parasite has mutated making it resistant to drugs.
The first-line treatment for malaria in many parts of Asia in the last decade has been a combination of dihydroartemisinin and piperaquine, also known as DHA-PPQ.
Researchers found in previous work that a strain of malaria had evolved and spread across Cambodia between 2007 and 2013 that was resistant to both drugs.
This latest research, published in The Lancet Infectious Diseases journal, found it has crossed borders and tightened its grip.
Almost 220 million people were infected with malaria in 2017, according to World Health Organisation estimates, and the disease killed 400,000 of them.
Via Sky News