Rubulavirus
If not vaccinated against mumps, susceptible individuals catch the disease by breathing around an infected person who has coughed or sneezed, releasing their contaminated saliva. Those who have had mumps are usually immune to future infections of the disease. Children have the highest risk of catching mumps, and it is rare for an adult to contract mumps. The incubation period for mumps can range from a couple weeks to a month, while the illness period is a few weeks. The swelling of the salivary glands is caused when the virus travels from the respiratory tract to the salivary glands and multiplies within the glands, causing the glands to swell.
Sialadenitis
Bacterial sialadenitis is uncommon nowadays and is usually associated with sialoliths. A study involving hospitals in the United Kingdom found that the incidence of admissions for sialadenitis is 27.5 per million of the population, with the most common cause being mumps which causes a viral infection in the salivary gland. Ascending acute bacterial parotitis used to be a common perimortal event but today this is no longer the case due to antibiotics and basic modern care which means that patients will be much less likely to become dehydrated.