One of a group of RNA viruses that are responsible predominantly for acute respiratory diseases and are usually transmitted in an airborne manner.

The paramyxoviruses include the agents of mumps, measles (rubeola), RSV (respiratory syncytial virus, which mainly afflicts children), Newcastle disease, parainfluenza, Sendai virus and Hendra virus.

Many of the paramyxoviruses cause disease in animals; such as, canine distemper and turkey rhinotracheitis.