A Study to Evaluate the Safety, Efficacy and Pharmacokinetics of Suraxavir Marboxil for Suspension

Suraxavir Marboxil will be administered as oral suspension: 40 mg (if weight ≥ 32 kg), or 20 mg (if weight \<32 kg).

Oseltamivir will be administered as oral granules: 30 mg (if weight ≤15 kg), 45 mg (if weight \> 15 kg to ≤ 23 kg), 60 mg (if weight \> 23 kg to ≤ 40 kg) or 75 mg (if weight \> 40 kg), twice daily (BID) for 5 days.