While less contagious than some viruses, the mumps virus is still contagious. It is most often transmitted when an infected person coughs or sneezes. The virus can cause symptoms similar to those seen in other medical conditions. Therefore, a doctor who suspects a person is infected may perform certain tests in order to rule out these conditions before making a definitive diagnosis.
The cause of mumps is an infection with the mumps virus. The virus is an RNA (ribonucleic acid) virus from the family Paramyxovirus and the genus Rubulavirus. The virus only infects humans, and mumps is considered less contagious than both measles and chickenpox.
The mumps virus is found worldwide; however, in the United States, mumps is relatively uncommon. Fewer than 300 cases were reported in 2003. (Prior to the mumps vaccine being licensed in 1967, 100,000 to 200,000 cases are estimated to have occurred in the United States each year.)
When infections do occur, they are more common in those living in close quarters, including:
- Military quarters
Infections with the mumps virus are most common during spring, especially April and May. Mumps appears to be happening more in adults, with approximately 40 percent of infections occurring in this group.
The mumps virus resides in the mucus in the nose and throat of the infected person, along with the saliva. When that person sneezes or coughs, droplets spray into the air. The infected mucus can land in other people's noses or throats when they breathe or put their fingers in their mouth, nose, or eyes after handling an infected surface.
Following transmission of the mumps virus, a person does not become immediately sick. Once the virus enters the body, it travels to the back of the throat, nose, and lymph glands in the neck, where it begins to multiply. The virus can also enter the blood and spread to the:
- Parotid gland
- Brain (meninges -- membranes that protect the brain and spinal cord)
- Testes or ovaries
After 12 to 25 days (the average is 16 to 18 days), symptoms of mumps can appear. This period between mumps transmission and the beginning of symptoms is called the "incubation period for mumps."
About 20 percent of people infected with the mumps virus do not develop symptoms. It is also thought that up to half of people infected with the virus do not develop the classic symptoms of mumps, such as swelling of the face and neck. Instead, they develop upper respiratory symptoms similar to the common cold.