Pharmacokinetics，Safety and Efficacy of ZSP1273 in Children 2-17 Years Old With Influenza A

Inclusion Criteria: 1. Subjects and their guardians who are able to understand the study and comply with all study procedures, and willing to provide written informed consent/assent prior to the predose examinations appropriately. 2. Male or female subjects aged ≥ 2 to ≤17 years at the time of signing the informed consent form. 3. Subjects with a diagnosis of influenza virus infection confirmed by all of the following: * Positive rapid antigen test (RAT) for influenza with nasal or throat swabs; * The time interval between the onset of symptoms and enrollment is 72 hours or less; * Fever ≥ 38ºC (axillary temperature); and at least one following respiratory symptoms associated with influenza virus infection is present Exclusion Criteria: 1. Subjects with severe influenza virus infection； 2. Subjects with any medical history in gastrointestinal that interferes with the absorption of drugs； 3. Immunodeficiency,including malignant tumor,organ or marrow transplant,human immunodeficiency virus \[HIV\] infection,or patients receiving immunosuppressant therapy 3 months prior to enrollment； 4. Have received any other investigational products within 3 months prior to dosing； 5. Positive urine pregnancy test； 6. Subjects with concurrent infections requiring antimicrobial therapy； 7. Subjects who are considered inappropriate for the study by the investigator.