 This study will evaluate the safety, tolerability, and systemic exposure of an experimental influenza flu treatment medication called DAS181. DAS181 is a dry powder that is administered via oral inhalation using a special device. Study participants will include healthy non-smoking males and females, ages 18-65. They will be given either DAS181 or placebo. Participants will remain in the clinic overnight to be watched for health changes for 24 hours after receiving the medication. Study procedures include: physical exams, chest x-rays, ECGs, lung function tests, collection of blood and urine samples, and throat swabs. Follow-up visits will occur on study days 2, 7, 14 and 30. 