The mumps virus is the most common cause of painful swelling of the parotid glands, which are salivary glands located between the ear and the jaw. This inflammation is also called parotitis or parotiditis.

But parotitis can also be caused by other viruses, including cytomegalovirus (CMV), and other conditions, including sarcoidosis, diabetes, Sjögren's syndrome, salivary gland tumors or stones, tooth problems, and bacterial infection.