Introduction
Influenza is an acute respiratory infection of influenza virus and a major cause of morbidity and mortality all over theworld. In particular,
elderly individuals and young children are at risk due to poor or weakened immune function.
Vaccination is usually used for the prevention of influenza virus infection but is not necessarily sufficient because viral mutagenesis occurs quickly, and dominant viral strains change annually.
Therefore it is desirable to enhance natural defenses by triggering
nonspecific innate immunity in daily life.
Fermented food including lactic acid bacteria (LAB) and their products
were known to contribute to maintain our health for a long time.
Recently, many LAB were selected as health promoting probiotics