<qa>  What is peramivir?This study will evaluate the safety and tolerability of peramivir, a new drug to treat influenza. The study will administer gradually increasing doses of the drug in successive small groups of subjects to determine the optimal dose that is safe and well tolerated. It will be studied first at a single dose and then in multiple doses. The study will also determine how long peramivir stays in the body and how high the drug levels are in the blood. 