Respiratory Virome Diversity and Baseline Immunity in Healthy Individuals in Shanghai

1\. Young Healthy Volunteers Inclusion Criteria: 1. Age between 20-35 years (inclusive), Han ethnicity, regardless of gender. Body Mass Index (BMI) between 19-26 kg/m² (inclusive), with a minimum weight of 50 kg for males and 45 kg for females. 2. The participant must be in good overall health, as determined by medical history, physical examination, vital signs, and results from a health checkup within the past year (normal or clinically insignificant findings). 3. Female participants must be non-pregnant and non-lactating. 4. Able to tolerate bronchoscopy and willing to provide nasal and pharyngeal swabs, as well as upper and lower respiratory secretions and peripheral blood samples. 5. Fully informed of the study's purpose, methods, and potential discomforts, with written informed consent provided, and willing to complete the study questionnaire. 6. Good compliance and willingness to follow the study protocol and complete follow-up procedures. Exclusion Criteria: 1. Non-permanent residents of Shanghai who have stayed in the city for more than 30 days; or permanent residents of Shanghai who have left the city within the past 30 days. 2. History of significant illness or major surgery within the past 30 days, or anticipation of major surgery during the study period. 3. Diagnosis of respiratory diseases (infectious or non-infectious) within the past 30 days, requiring medication (oral, inhaled, or nebulized). 4. Presence of clinically significant diseases or factors, including but not limited to neurological, cardiovascular, hematologic, hepatic, renal, gastrointestinal, respiratory, metabolic, endocrine, immune, skeletal diseases, or other conditions deemed unsuitable by the investigator. 5. Long-term use of medication. 6. Positive test results for HIV antibodies (HIV-Ab), hepatitis B surface antigen (HBsAg), hepatitis C antibodies (HCV-Ab), or syphilis antibodies (TP-Ab). 7. Participation in any drug or medical device clinical trial within the past 3 months. 8. Vaccination within the past 30 days or planned vaccination during the study period. 9. Any other condition deemed by the investigator to impact the participant's ability to provide informed consent, follow the protocol, or affect study outcomes or the participant's safety. 2\. Elderly Healthy Volunteers Inclusion Criteria: 1. Age between 60-75 years (inclusive), Han ethnicity, regardless of gender. Body Mass Index (BMI) between 19-26 kg/m² (inclusive), with a minimum weight of 50 kg for males and 45 kg for females. 2. The participant must have a healthy respiratory system, as determined by medical history, physical examination, vital signs, and results from a health checkup within the past year (normal or clinically insignificant findings). 3. Able to tolerate bronchoscopy and willing to provide nasal and pharyngeal swabs, as well as upper and lower respiratory secretions and peripheral blood samples. 4. Fully informed of the study's purpose, methods, and potential discomforts, with written informed consent provided, and able to independently complete the study questionnaire. 5. Good compliance and willingness to follow the study protocol and complete follow-up procedures. Exclusion Criteria: 1. Non-permanent residents of Shanghai who have stayed in the city for more than 30 days; or permanent residents of Shanghai who have left the city within the past 30 days. 2. History of significant illness or major surgery within the past 30 days, or anticipation of major surgery during the study period. 3. Diagnosis of respiratory diseases (infectious or non-infectious) within the past 30 days, requiring medication (oral, inhaled, or nebulized). 4. Presence of abnormal respiratory system function or other clinically significant diseases or conditions. 5. History of malignant tumors (including hematologic malignancies or solid tumors). 6. Long-term use of medication. 7. Positive test results for HIV antibodies (HIV-Ab), hepatitis B surface antigen (HBsAg), hepatitis C antibodies (HCV-Ab), or syphilis antibodies (TP-Ab). 8. Participation in any drug or medical device clinical trial within the past 3 months. 9. Vaccination within the past 30 days or planned vaccination during the study period. 10. Any other condition deemed by the investigator to impact the participant's ability to provide informed consent, follow the protocol, or affect study outcomes or the participant's safety.