Mother's Croup Reveals That Parainfluenza Virus Is the Cause of Her Son's Viral Parotitis.

In modern practice viral parotitis is unlikely to be due to mumps. Case and surveillance studies have detected a host of other viruses in mumps-negative viral parotitis, but because of their weak association with viral parotitis, it has been difficult to establish causality. This case report is unique because a familial pair presented in tandem with different manifestations of an infection with the parainfluenza virus. These circumstances allowed the strong association of the parainfluenza virus with the mother's croup to be substituted for the normally weak association of the parainfluenza virus with the son's viral parotitis. This strongly inferred that the parainfluenza virus caused the patient's viral parotitis and provides the best evidence to date of a virus other than mumps causing viral parotitis.