Video report by ITV News Correspondent Lucy Watson
In most areas of combating diseases, advances are being made all the time, but malaria is fighting back.
Malaria parasites, which have developed resistance to key drugs, have spread rapidly across South East Asia, according to UK and Thailand researchers.
Studies in the Lancet Infectious Diseases Journal showed the parasites have moved from Cambodia to Laos, Thailand and Vietnam, where half of patients are not being cured by first-choice drugs.
"These worrying findings indicate that the problem of multi-drug resistance in P falciparum has substantially worsened in south-east Asia since 2015," said Olivo Miotto from the Wellcome Sanger Institute and University of Oxford, who co-led the study.
"This highly successful resistant parasite strain is capable of invading new territories and acquiring new genetic properties," he added.
There is a major concern is that the mutated strain could spread to Africa, where over 90% of malaria cases and deaths occur.
How is malaria currently being treated?
Malaria is treated with a combination of two drugs - artemisinin and piperaquine, which was introduced in 2008 in Cambodia.
Mosquito nets and anti-mosquito repellents have also been used in attempts to deter the parasites.
But by 2013, the first cases of the parasite mutating and developing resistance to both drugs were detected in western parts of the country.
According to the journal, the drug-resistant gene had spread across the countries, with some areas exceeding 80% of the local parasite population.
Die from Malaria each year, including most children in Africa.
What is being done?
In the meantime, Cambodia, Laos, and Vietnam have implemented malaria control programmes to monitor the drug-resistant gene.
According to a report by the WHO, the countries are collecting data on malaria cases on a monthly basis and updating a regional web-based platform.
The Lancet journal recommends the Greater Mekong Subregion countries form a coordinated strategy across the whole region, rather than hold country-specific programmes.
Is it as bad as it sounds?
Dr Pascal Ringwald from the WHO told ITV News: “We have not seen a spread form South East Asia to Africa or to another another part of the world."
"The fact that malaria is decreasing in the Great Mekong is going to reduce the risk of spread.”
the reported number of malaria cases fell by 75% in the Greater Mekong Subregion between 2012 and 2017. Malaria deaths fell by 93% over the same period.
However, their studies have shown that malaria cases increased over 32% in some areas, and more cases are being reported in regions where there were little to no reports in previous years.
The WHO attributed this to a number of factors, including stock-outs of antimalarial drugs, delays in rollout for drug treatments, low utilisation of mosquito nets, and increased population movement.
They have also pointed out that new technologies lead to more reported cases in remote areas where there weren't capabilities to collect data on the disease before.