Materials and methods are provided for treating influenza B infections in humans. Anti-human influenza virus monoclonal antibodies and antigen-binding fragments thereof having a neutralization activity against a human influenza B virus are provided. Methods for producing anti-human influenza B virus monoclonal antibodies are also provided. The antibodies and antigen-binding fragments thereof can be effective against a wide range of influenza B viral strains. Methods of inhibiting or treating a human influenza B infection are provided. The anti-influenza B therapeutics can also be used to manufacture medicaments effective against influenza B infections, to detect human influenza B in a human subject, for use in pharmaceutical compositions, and for use in kits for at least one of the prevention, the treatment, and the detection of human influenza B in a human subject.