Parainfluenza virus (PIV) is a negative-sense single-stranded RNA virus in the Paramyxoviridae family. There are 4 serotypes that follow seasonal patterns with varying rates of infection for each serotype. PIV is an established cause of disease and death in the pediatric and immunocompromised populations, and its impact on the hospitalized adult is becoming more apparent with the increased use of multiplex molecular assays in the clinical setting. The clinical presentation of PIV in hospitalized adults varies widely and includes upper respiratory tract infections, severe lower respiratory tract infections, and exacerbations of underlying disease; 0.2%-11.5% of hospitalized patients with pneumonia have been found to have PIV infection. Currently no licensed treatment is available for PIV infection. Ribavirin has been used, but case studies show no impact on mortality rates. DAS181, an inhaled sialidase, is undergoing clinical development for the treatment of PIV in adults and children.