Li Guiqiao, a professor at the Tropical Medicine Institute at Guangzhou University of Traditional Chinese Medicine, said he first used artemisinin on malaria patients when he was a village doctor in China's Yunnan province in 1974, at the government's request. Within hours, all 18 of his test patients felt better, and all recovered within a few days, Li said.
The leaves of the Artemisia annua -- sweet wormwood shrub -- have been used by Chinese herbalists as malaria medicine for more than 1,500 years, but in the late 1960s, scientists discovered its anti-malarial properties. Worldwide experts today believe artemisinin to be the most effective malaria drug.
However, after the WHO announced in 2001 that artemisinin should be used in combination with other drugs to slow drug resistance, the herbal shrub has been in short supply. Steep prices for the drug and a shortage of WHO-approved suppliers have led to the production of counterfeit artemisinin drugs, which have been implicated in a number of deaths.
"Fake drugs are all over the place and they are really creating problems in Asia," said Kevin Palmer, regional adviser for malaria in the Western Pacific at the WHO. "We are afraid they might get into Africa too as demand increases."
Though officials have begun spot-testing artemisinin drugs in the field, many counterfeits have reached the market.
"[Artemisinin drugs] are easy to fake," Palmer said. "Ninety-seven percent of fakes seized are just chalk. It's very worrying ... someone is making millions."
According to Wichai Satimai of the Public Health Ministry in Thailand -- where fake drugs are common -- counterfeit drugs aren't just a rip-off; they can also cause serious health consequences.
"Fake drugs cause complications and higher mortality," Wichai said. "If the drug is sub-standard -- say it has only 50 percent of the active ingredient -- it can't kill the whole protozoa (parasite). It will produce drug resistance."
With supplies already tight, the WHO has also only accredited two suppliers of official artemisinin-based combination therapies (ACTs) -- Swiss drug firm Novartis AG and Guilin Pharmaceuticals Company, based in China's southwestern city of Guilin.
Developing countries such as those in sub-Saharan Africa -- where 90 percent of the world's malaria deaths occur -- must purchase ACTs from those two suppliers in order to use money from the UN's Global Fund to Fight AIDS, Tuberculosis and Malaria. Critics have called for China and Vietnam to grow more artemisinin to help supply world demand, and for the WHO to accredit more manufacturers of ACTs.