Sendai virus (SeV), previously also known as murine parainfluenza virus type 1 or hemagglutinating virus of Japan (HVJ) is a negative sense, single-stranded RNA virus of the family Paramyxoviridae. SeV is a member of genus Respirovirus, members of which primarily infect mammals.

SeV induces lesions within the respiratory tract, usually associated with bacterial inflammation of the trachea and lung (tracheitis and bronchopneumonia, respectively). However, the lesions are limited. Detection of SeV-specific antigens in several serological methods, including ELISA,immunofluorescence, and hemagglutination assays, with particular emphasis on use of the ELISA for its high sensitivity and its fairly early detection.