A method for treating an influenza virus infection is described. The disclosed method generally involves administering an effective amount of a compound (A), for example baloxavir marboxil, and a compound (B), for example a neuraminidase inhibor, to a subject that (1) has an influenza virus infection, (2) has been symptomatic of the influenza virus infection for no more than 96 hours, and (3) further has at least one severe influenza condition selected from the following: (a) being hospitalized due to severe influenza virus infection, (b) requiring an extension of hospitalization because of the influenza virus infection during the hospitalization, (c) having a National Early Warning Score 2 of four or more, (d) being on support for respiration, and (e) having at least one complication attributable to the influenza virus infection that necessitates hospitalization.