Paramyxoviridae are responsible for some serious diseases eg Distemper, Rinderpest, Newcastle disease. Their control by vaccination/hygiene has been a veterinary success although they all remain endemic to parts of Africa and India. Respiratory syncytial virus cannot be well controlled by vaccination and it is the major cause of croup in babies and of respiratory diseases in calves.

Derivations: para = by the side of, or related in structure, but not antigenically, to the orthomyxoviridae:- (they both are the same size and have zipper-like capsids of nucleoprotein (NP) and haemagglutinin spikes); pneumo = death from expire; morbilli = disease.