A group of viruses that belong to the genus Paramyxovirus of the family Paramyxoviridae. The family includes two other genera, Morbillivirus and Pneumovirus. The genus Parainfluenza includes viruses such as mumps and Newcastle disease (in fowl and humans). Measles virus is a member of the genus Morbillivirus, and respiratory syncytial virus belongs to the genus Pneumovirus. Related members exist in nonhuman species; human measles virus is related to canine distemper and bovine rinderpest virus. Simian and bovine parainfluenza viruses also are known.