The viruses produce a characteristic syncytia formation, hence the name. There is only one serotype that affects humans. These viruses generally produce local infections in the upper and lower respiratory tract. The virus can be shed over 3-16 days and the main pathologic response is inflammation. The severe diseases occur most often with types 1 and 2.
Mumps is a systemic infection spread by viremia.
The major targets include glandular and nervous tissue. The virus enters via the pharynx or conjunctiva, there is local multiplication followed by viremia. A secondary viremia disseminates the virus to salivary glands, testes, ovaries, pancreas and the brain. The most characteristic response is painful enlargement of the parotid glands. Severe cases may progress to include epididymoorchitis in prepubescent males, which can cause atrophy of the testes, but rarely sterility.