A Surveillance Study of Susceptibility to Baloxavir Marboxil in Participants With Influenza

Inclusion Criteria:

• Participants with symptoms suggestive of influenza with diagnosis confirmed by apositive local influenza test within 24 hours before full study screening.

• Participants with a negative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test within 48 hours before full study screening.

• Time interval between onset of influenza symptoms and the pre-dose examinations atscreening is 48 hours or less

Exclusion Criteria:

• Participants with severe influenza virus infection requiring inpatient treatment.

• Severely immunocompromised participants [including participants receivingimmunosuppressant therapy, or those with cancer or human immunodeficiency virus (HIV) infection] as defined by the investigator.

• Participants with concurrent (non-influenza) infections requiring systemicanti-microbial and/or anti-viral therapy at the pre-dose examinations.

• Treatment with baloxavir marboxil, peramivir, laninamivir, oseltamivir, zanamivir,rimantadine, umifenovir or amantadine within 30 days prior to screening.

• Treatment with an investigational influenza-specific monoclonal antibody within 6months or 5 half-lives, whichever is longer, prior to screening.

• Treatment with an investigational therapy within 30 days or 5 half-lives, whicheveris longer, prior to screening.

• Known hypersensitivity to baloxavir marboxil or the drug product excipients.

• Females who have commenced menarche (i.e., child-bearing potential).