Researchers in Thailand are warning that a drug-resistant strain of malaria is emerging.
The new strain is especially resistant to artesunate drugs, one of the world's most common treatment for malaria.
Researchers first noticed artesunate was not working in some patients along the Thai-Cambodian border, according to Al Jazeera's Aela Cullen.
"Experts blame incorrect diagnosis leading to the overprescription of malaria-fighting drugs," she said.
The developments come as the World Health Organisation announced on Tuesday that increased funding is starting to pay off in the battle against malaria.
The WHO said in its World Malaria Report 2009 that "significant progress" had been made in the delivery of mosquito nets and malaria drugs due to an increase in funds totalling $1.7bn in 2009 from $0.3bn in 2003.
Call for funds
But the WHO said $5bn more was needed every year to get maximum global impact worldwide.
Malaria infected more than 240 million people last year and killed an estimated 863,000 people, mostly in Africa.
"We're concerned and have been concerned for sometime now"
Robert Newman, director of the global malaria programme at the WHO
Repeated attempts to eradicate the disease have flopped and until recently, the number of cases has been rising.
Robert Newman, the director of the global malaria programme at the WHO, told Al Jazeera from Geneva, Switzerland that the new drug-resistant strain had raised concern.
"We're concerned and have been concerned for sometime now," he said.
"The WHO has been leading an effort along with a number of international partners and local governments in containing the spread of this drug-resistant parasite."
'Urgency not emergency'
But Newman added that the strain would be classified as an "urgency rather than an emergency".
"We're not really seeing patients dying from this strain and the problem remains relatively localised," he said.
"And the strategy to contain it is clear. We need to diminish the burden of parasites in the region by bringing all of our preventive measures to bear.
"And we need to correctly diagnose malaria and make sure that patients are treated with correct medications.
"We do need to make sure that we're focusing on South-east Asia and it has received less funding than other regions. However, the bulk of the burden of malaria has remained in Africa, so those resources spent [there] are certainly appropriate."
Source: Al Jazeera