Final answer:
The mumps virus, a paramyxovirus, causes parotitis, which is the inflammation of the parotid glands commonly seen in the contagious viral infection called mumps.
Step-by-step explanation:
The virus that causes parotitis, which is the inflammation of the parotid glands, is the mumps virus. Parotitis is commonly associated with the disease known as mumps, which is a contagious viral infection characterized by swelling of the parotid salivary glands. The mumps virus is a paramyxovirus and it is also known for its envelope that has both hemagglutinin and neuraminidase spikes, which are essential for the virus to attach to and enter host cells. A fusion protein on the surface of the virus helps it to merge its envelope with the plasma membrane of the host cell, thus facilitating infection.