What causes mumps?

A. Fungus
B. Bacterium
C. Deficiency of vitamins
D. Virus

Mumps is due to an infection by the mumps virus. It can be transmitted by respiratory secretions (e.g. saliva) from a person already affected with the condition. When contracting mumps, the virus travels from the respiratory tract to the salivary glands and reproduces, causing the glands to swell