<qa>  What is the average dose of oseltamivir?Upon meeting certain screening criteria, participants will be randomly assigned to receive oseltamivir either at a standard-dose level 75 mg twice daily orally or equivalent dose adjusted for age, weight, and kidney function or at a high-dose level 150 mg twice daily orally or equivalent dose adjusted for age, weight, and kidney function. Treatment will continue for 5 days, after which participants who meet clinical failure criteria will continue their assigned treatment for an additional 5 days. It is anticipated that participants will remain hospitalized through the course of treatment. On Day 0, which marks the first day of hospitalization, participants will undergo a medical review, physical examination, blood sampling, nasal swab, throat swab, anal swab, and chest x-ray. An endotracheal aspirate procedure and urine sampling may also be performed. During the hospital stay, most of the above procedures will be repeated regularly, and additional samples of lung fluid, cerebral spinal fluid, and pleural fluid may be obtained. On Day 5 and possibly on Day 10, participants will undergo a follow-up x-ray. If applicable, participants will attend outpatient study visits on Days 10, 14, and 28 for further evaluation; participants with avian influenza will also attend visits on Days 56 and 180. 