Inclusion Criteria:

• An individual must meet all of the following criteria to be eligible for study participation:
• 1. Greater than or equal to 18 and less than or equal to 50 years of age.
• 2. Able to provide consent.
• 3. Agrees to not use tobacco products, marijuana, or vaping products during participation in this study.
• 4. Willing to remain in isolation for a minimum of 10 calendar days (or for the duration of viral shedding) and to comply with all study requirements.
• 5. A male subject is eligible for the study if he meets one of the following criteria, beginning at least 4 weeks prior to enrollment and continuing until 10 weeks after administration of the human challenge virus and follow-up visit #4:
• 1. Is infertile, including history of successful vasectomy.
• 2. Agrees to practice abstinence.
• 3. Agrees that, with heterosexual intercourse with a fertile female partner, he will use a condom with spermicide and his female partner (including those who have undergone bilateral tubal ligation) will use an acceptable form of contraception (see inclusion criterion 6c).
• 6. A female participant is eligible for this study if she is not pregnant or breastfeeding and meets one of the following criteria, beginning at least 4 weeks prior to enrollment and continuing until 10 weeks after administration of the human challenge virus and follow-up visit #4:
• 1. Is infertile, including postmenopausal status (as defined by no menses for greater than or equal to 1 year) or history of hysterectomy.
• 2. Agrees to practice abstinence.
• 3. Agrees that, with heterosexual intercourse with a fertile male partner, she will use an acceptable form of contraception and her male partner will use a condom with spermicide. Acceptable effective methods of female contraception include the following: bilateral tubal ligation, implant of levonorgestrel, injectable progestogen, intrauterine device, oral contraceptive pills, and diaphragm with spermicide.
• 7. Willing to have samples stored for future research.
• 8. Human immunodeficiency virus (HIV) uninfected with a negative test within 60 days of inoculation (Day 0).

Exclusion Criteria:

• An individual meeting any of the following criteria will be excluded from study participation:
• 1. Has self-reported or medically documented significant medical condition including but not limited to:
• 1. Chronic pulmonary disease (e.g., asthma, emphysema).
• 2. Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects).
• 3. Chronic medical conditions requiring close medical follow-up or hospitalization during the past 5 years (e.g., insulin-dependent diabetes mellitus, renal dysfunction, hemoglobinopathies).
• 4. Immunosuppression or ongoing malignancy.
• 5. Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures).
• 6. Post-infectious or post-vaccine neurological sequelae.
• 2. Has close or household (i.e., share the same apartment or house) high-risk contacts including but not limited to:
• 1. Persons greater than or equal to 65 years of age.
• 2. Children less than or equal to 5 years of age.
• 3. Residents of nursing homes.
• 4. Persons of any age with significant chronic medical conditions such as:
• * Chronic pulmonary disease (e.g., asthma).
• * Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects).
• * Chronic medical conditions requiring medical follow-up or hospitalization during the past 5 years (e.g., insulin-dependent diabetes mellitus, renal dysfunction, hemoglobinopathies).
• * Immunosuppression or cancer.
• * Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures).
• * Persons who are receiving long-term aspirin therapy.
• * Women who are pregnant, trying to become pregnant, or breastfeeding.
• 3. Has a body mass index (BMI) less than or equal to 18.5 or greater than or equal to 35.
• 4. Smokes more than 4 cigarettes or other tobacco products on a weekly basis or any type of vaping/e-cigarette use more than 4 times per week.
• 5. History of facial reconstructive procedures or nasopharyngeal malformation.
• 6. Positive for Hepatitis B or Hepatitis C infections.
• 7. Complete blood count (CBC) with differential outside of the NIH Department of Laboratory Medicine (DLM) normal reference range and deemed clinically significant by the PI.
• 8. Grade 2 or higher Hemoglobin for female participants or Grade 1 or higher Hemoglobin for male participants.
• 9. Chemistries in the acute care, mineral, and/or hepatic panels, and/or any of the following: lactate dehydrogenase (LDH), uric acid, creatine kinase, and total protein outside of the NIH DLM normal reference range and deemed clinically significant by the PI.
• 10. Urinalysis outside of the NIH DLM normal reference range and deemed clinically significant by the PI.
• 11. Clinically significant abnormality as deemed by the PI on ECG.
• 12. Clinically significant abnormality as deemed by the PI on ECHO.
• 13. Clinically significant abnormality as deemed by the PI on the PFT and/or spirometry.
• 14. Recent acute illness within 1 week of admission to the NIH CC.
• 15. Known allergy to any component of the interventional agent.
• 16. Known allergy to treatments for influenza (including but not limited to oseltamivir, nonsteroidals).
• 17. Known allergy to 2 or more classes of antibiotics (e.g., penicillins, cephalosporins, fluoroquinolones, or glycopeptides).
• 18. Receipt of influenza vaccine within 8 weeks prior to enrollment.
• 19. Receipt of blood or blood products (including immunoglobulins) within 3 months prior to enrollment.
• 20. Receipt of any unlicensed drug within 3 months or 5.5 half-lives (whichever is greater) prior to enrollment.
• 21. Receipt of any unlicensed vaccine within 6 months prior to enrollment.
• 22. Self-reported or known history of current alcoholism or drug abuse, or positive urine/serum test for drugs of abuse (i.e., amphetamines, cocaine, benzodiazepines, opiates, or metabolites, but not tetrahydrocannabinol or metabolites).
• 23. Self-reported or known history of psychiatric or psychological issues deemed by the PI to be a contraindication to protocol participation
• 24. Known close contact with anyone known to have influenza in the past 7 days.
• 25. Known close contact with anyone known to have COVID-19 in the past 14 days.
• 26. History of COVID-19-related complications, including, but not limited to: inpatient hospitalization, required the use of oxygen, and/or on-going sequelae.
• 27. Non-English speaking participants.
• 28. Any condition that, in the judgment of the PI, is a contraindication to protocol participation or impairs the volunteer s ability to give informed consent.