- 1. Age ≥5 years; Body weight <120 kg ; documented fever (axillary temperature >37.5o C) or history of fever during the previous 48 hours in the absence of another obvious cause of fever, such as pneumonia, otitis media, etc ; Monoinfection with P. vivax with parasitemia between 250 and 100,000 asexual parasites/µl as determined by microscopic examination of thick and thin peripheral blood smears ; Informed consent from the patient or parent/guardian (for those <18 years), assent from child (ages 7 to 17 years inclusive), patients 5 through 6 years old will not need an assent ; Willingness on the part of the patient to return to the clinic and/or receive home visits for regular check-ups during the 6-month (168 days) follow-up period ; Place of residence within 30-45 minutes of study site.