The purpose of this study is to determine whether drinking pasteurized milk (milk heated to kill harmful germs) that contains inactive particles of a flu virus called A(H5) could lead to the detection of the virus in the nose or throat. Inactive particles are not capable of causing disease. The results will help the Centers for Disease Control and Prevention (CDC) better understand how milk consumption could affect flu surveillance. Investigators also want to see if the body produces antibodies in response to this milk consumption.

Since March 2024, avian influenza A (H5N1) viruses have infected U.S. dairy cattle and spread widely. The virus has been identified in high concentrations in raw milk, and research shows that pasteurization - the process of heating milk to a specific temperature for a set time - inactivates the A (H5N1) virus. Therefore, the Food and Drug Administration (FDA) says that commercial pasteurized milk is safe for consumption. However, trace amounts of inactive influenza particles may still be detected in pasteurized milk.

This study aims to determine whether drinking pasteurized milk could be a possible exposure for H5N1 influenza detection. The findings will support the Centers for Disease Control and Prevention's (CDC) efforts to evaluate milk consumption as a factor in influenza surveillance and provide context for interpreting surveillance data.

Healthy adults will drink 250 mL of pasteurized milk containing the inactive H5N1 virus, provided by the CDC, either during a single visit or over three consecutive daily visits. Nasal and combined nasal/oral swabs will be collected immediately following milk consumption to assess the presence of influenza. Additionally, a subset of participants will provide blood, saliva, and stool samples at the initial visit and again 21-30 days post-consumption.

Inclusion Criteria:

• Individuals aged 18-64 years
• BMI ≤ 35 kg/m2
• Able to understand and give informed consent (American English) and comply with study visits and procedures.
• In good general health based on medical history and the investigator's clinical judgment.

Exclusion Criteria:

• Symptoms of acute respiratory illness or conjunctivitis within 7 days
• Febrile illness in the previous 72 hours
• Recent influenza antiviral use (within 14 days)
• Immunosuppression due to illness or medications
• Current pregnancy or breastfeeding
• History of allergy or intolerance to milk or milk alternatives
• Consumption of raw (unpasteurized) milk within the previous 14 days
• Recent work (within 14 days) on a farm with animals known to be infected with A(H5) virus
• Previous receipt of A(H5) vaccine at any time

The research team will share deidentified respiratory testing results.

The team will share the data immediately following the study publication, or at the end of the study analysis if not published, with no end date.

Data will be available for access in a public database such as Dataverse.