Evidence suggests the great killer malaria is developing greater resistance, as Channel 4 News hears it could mean many more cases across south east Asia.
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Doctors have warned that a form of drug-resistant malaria, once contained to Cambodia, has now been detected on the border of Thailand and Burma.
Writing in the medical journal, The Lancet, the doctors from Britain and Thailand, say that there is now an urgency to prevent it spreading further and potentially killing millions of people.
The malaria parasite, Plasmodium falciparum, is responsible for nine out of 10 malaria deaths. Frontline treatment is the drug artemisinin and in Thailand has been used in conjunction with other medications for years to treat the disease.
The 10-year study followed more than 3,000 patients. The time it took the drug to reduce the number of parasties in the blood by half rose from 2.6 hours to 3.7 hours. In real time, that means that patients who were being treated within two days are now taking up to four or five days.
Professor Francois Nosten, director of the Shoklo Malaria Research Unit in Thailand, told Channel 4 News, that the consequences of this could be that it transmits more easily between patients and the number of cases could increase.
In the 1950s, the then frontline drug Chloroquine failed and the disease spread from Cambodia, through Asia to Africa, killing millions of children.
Professor Nicholas White, of the Mahidol Oxford Tripical Medicine Research Unit in Bangkok, said the disease was not being taken seriously at either nation or international level.
We are not dealing with this with the same vigour if it was affecting richer countries. Prof Nicholas White
"There is indeed a lot of activity, there is a global plan but it's not being considered in the same way as we might consider H15N1 influenza or Sars. We are not dealing with this with the same vigour if it was affecting richer countries."
The researchers expect to know within the year whether the cases in Thailand-Burma have the same genetic make up as the Cambodian Plasmodium falciparum.
But they will also be looking atissues such as economic migration, the failure to take the anti-malarial drugs correctly and the flood of counterfeit drugs into the region.