Artemisinin Resistance in Cambodia II

Inclusion Criteria: 1. Acute symptomatic falciparum malaria infection as determined by malaria smear with a parasite density of 1000 to 200,000 asexual parasites/Micro-liter as determined on the thick/thin screening smear with fever (defined as ≥ 37.5ºC), or reported history of fever within the last 48 hours. 2. Age: 18-65 years old 3. All females between the age of 18 and 50 are required to have a negative human chorionic gonadotropin (hCG) pregnancy test (urine). All females of childbearing potential (not surgically sterile, or less than two years menopausal) are required to use an acceptable method of contraception, such as implant, injectable, or oral contraceptive(s), if possible with additional barrier contraception, intrauterine device, sexual abstinence, or vasectomized partner, throughout the study. 4. Written informed consent obtained 5. Willing to stay under close medical supervision for the study duration of 42 days 6. Otherwise healthy Out-patients Exclusion Criteria: 1. Pregnant women, nursing mothers, or women of childbearing potential who do not use an acceptable method of contraception (as described in Inclusion Criteria, # 3) 2. Mixed malaria infection on admission by malaria smear 3. A previous history of intolerance or hypersensitivity to the study drug artesunate or to drugs with similar chemical structures, such as artemether, artemisinin or dihydroartemisinin 4. History of malaria drug therapy administered in the past 30 days 5. Previous participation in this trial, or participation in any other studies involving investigational or marketed products, concomitantly or within 30 days prior to entry in the study 6. History of significant cardiovascular, liver or renal functional abnormality or any other clinically significant illness, which in the opinion of the investigator would place them at increased risk. 7. Symptoms of severe vomiting (no food or inability to take food during the previous 8 hours). 8. Signs or symptoms of severe malaria (adapted from WHO recommendations (2003): prostration, impaired consciousness, respiratory distress, convulsions, systolic blood pressure \< 70 mm Hg, abnormal bleeding, severe anemia with hemoglobin \< 8 g/dL or HCT \< 24%, hyperparasitemia at \> 4% parasitized red blood cells). 9. Unable and/or unlikely to comprehend and/or follow the protocol