inclusion criteria: group a - yellow fever - ability to provide written informed consent - males and nonpregnant, non-breast-feeding females, aged 18 years or older - subject weight ≥ 50 kg (110 lb.) - positive test for yfv by molecular amplification of the virus in the blood - first onset of symptoms of yf occurring within the previous 7 days - male and female subjects must agree to the contraception requirements and must meet the inclusion criteria regarding contraception as outlined in the protocol - clcr of at least 60 ml/min by cockcroft-gault equation - ast < 5000 u/l - indirect bilirubin < 1.5 mg/dl - neutrophil count < 7500 /mm3 - international normalized ratio (inr) < 1.5

inclusion criteria: group a - yellow fever - ability to provide written informed consent - males and nonpregnant, non-breast-feeding females, aged 18 years or older - subject weight ≥ 50 kg (110 lb.) - positive test for yfv by molecular amplification of the virus in the blood - first onset of symptoms of yf occurring within the previous 7 days - male and female subjects must agree to the contraception requirements and must meet the inclusion criteria regarding contraception as outlined in the protocol - clcr of at least 60 ml/min by cockcroft-gault equation - ast < 5000 u/l - indirect bilirubin < 1.5 mg/dl - neutrophil count < 7500 /mm3 - international normalized ratio (inr) < 1.5