This study will be a double-blind, randomized, placebo-controlled study of a single dose (20mg) of Influenza Antiviral DAS181-F04 for 3 days. The group of nine subjects will be randomly assigned to DAS181 or placebo at 2:1 ratios. Subjects will be admitted to the inpatient clinic at a minimum of the night prior to first dose. The subjects will stay in the inpatient clinic for the duration of dosing and one day after dosing, they will be required to come back for follow-up visits on study days 4, 6, 9, 16 (+/-1 day), 32 (+/-3 days), and 90 (+/-10 days). The safety parameters will include abnormal laboratory values, adverse events and clinical observations.

This study will be a double-blind, randomized, placebo-controlled study. The subjects will receive a single-dose treatment of DAS181-F04 or placebo at a targeted delivered dose of 20mg each day for three days. The subjects will be evaluated on the day before the initial dose (Day -1) and randomly assigned to DAS181-F04 or placebo in a 2:1 ratio. Subjects will be evaluated prior to dosing on Days 0, 1 and 2. Additional follow-up evaluations will occur one day after completion of dosing (Day 3) and on Days 4, 6, 9, 16 (+/-1 day), 32 (+/-3 days) and 90 (+/-10 days). The primary objective is to determine the safety and tolerability of DAS181-F04 encapsulated dry powder compared to placebo when administered by oral inhalation using a dry powder inhaler (DPI) in healthy adults. The secondary objective is to investigate the pharmacokinetic and immunologic profile of DAS181 encapsulated dry powder dose to dose and compared to placebo when administered by oral inhalation using a DPI in healthy adults. A total of 9 subjects, healthy male and female subjects, ages 18 to 45 years will be enrolled. Subjects will be randomized 2:1 ratio, wherein 6 subjects will receive the active drug and 3 subjects will receive placebo. Subjects may be replaced if a subject withdraws within 7 days (Day 9) after receipt of the final study drug dose.

Inclusion Criteria:

-Male and female subjects in good health in the opinion of the site Principal Investigator (PI) or sub-investigator as determined by vital signs, medical history, and a physical exam. -Subjects must be able to verbalize understanding of the consent form, provide written informed consent and verbalize willingness to complete study procedures. -Be 18 to 45 years of age (inclusive), at the time of screening. -Subjects must have a Body Mass Index (BMI) of 17.5-35. Actual lower weight limit may be 50 kg, if BMI is in the range indicated. -No history of smoking in the past six months, regardless of clinical relevance. -Electrocardiogram (ECG) with no clinically significant abnormalities recorded at screening visit: PR interval within 120 and 200ms, QRS interval < 120ms, and confirmed QTc interval \