Mumps

Mumps is a contagious viral disease which blocks the drainage of the salivary glands, causing them to swell and giving the patient the swollen face which lends the disease its name. Although mumps is very contagious and virulent, it's relatively harmless and rarely results in the death of the patient, particularly when the patient is a child. The disease is somewhat more serious in adults where in rare cases it can lead to sterility.
The disease will pass of its own accord in 10-14 days. Patients respond well to rest, fluids, and being reassured. People who have not had the disease should avoid anyone with it to prevent contagion.