Causes and Risk Factors of Mumps

Mumps infection is caused by a virus that is easily transmitted through casual contact. Infection with mumps is not common because many people are vaccinated. However, you can get the infection if you have not been vaccinated, or, in rare instances, if you are not immune even after having been vaccinated.

mumps causes and risk factors
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Common Causes 

Mumps is caused by a virus that enters the body through the mucous membranes, which are the areas that line the inside of your mouth, nose and throat. The virus that causes mumps is a paramyxovirus.  

How Paramyxovirus Spreads

The virus can survive in respiratory fluids, and this is how it is transmitted from person to person. Respiratory droplets can spread the virus through routine occurrences such as coughing and sneezing.

You can also catch the virus if you touch objects that have the virus on them. Sharing cups, utensils, and other objects, or being in close contact with someone who has mumps can also increase your chances of getting the infection. Lack of good hygiene, such as inadequate hand washing, can increase the spread of the virus.

Mumps has an incubation period, which means that after you become infected with the virus it takes time for symptoms of the illness to develop. The incubation period for mumps is about two to three weeks.

Because of the incubation period, you can catch the virus from someone who does not yet know that they have it and, similarly, you can spread the virus to others even if you do not know that you have it.

How Mumps Causes Illness

The paramyxovirus causes an immune reaction as the body tries to fight it, which exacerbates the effects, causing flu-like symptoms and the characteristic swelling of the face and neck.

It is also described as a neurotrophic virus, which means that it has a tendency to travel to the nervous system.

Up to 50% of people infected with mumps have been shown to have an increase in cells in their spinal fluid, with a much smaller percentage of patients experiencing clinical symptoms of meningitis (infection of the protective covering of the brain) or encephalitis (infection of the brain itself).

The virus can also affect other parts of the body, including the pancreas and testes, causing painful enlargement and swelling of these areas.

Rare Causes and Risk Factors

There are certain conditions and situations that can predispose you to develop mumps. However, the illness can develop unexpectedly, despite the fact that it is not very common.

Mumps in Vaccinated People

Mumps infection can develop in people who were vaccinated.

Even if you received proper vaccination for mumps, you can still become infected.

This is because the vaccine, while highly effective, is not 100% effective in every person. It is believed to be about 88% effective at producing immunity. So when most people get vaccinated, the infection becomes less prevalent in the community, producing what is described as herd immunity.

Herd immunity is the tendency for an infection to decrease in the population, as groups of people who have been vaccinated are less likely to get and spread the infection.

Yet, once in a while, people who were vaccinated can become infected. It is believed that your infection may be milder if you have been vaccinated, but that point is not completely clear.

Immune Deficiency After Vaccination

If you develop an immune deficiency due to immunosuppressive medications, cancer, or a disease that affects your immune system, you might become predisposed to a mumps infection even if you had been vaccinated and immune to the infection in the past. Talk to your healthcare provider to decide if it is important to be revaccinated.

Mumps Healthcare Provider Discussion Guide

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Doctor Discussion Guide Child

Babies Born to Infected Mothers

While it is not common, women who become infected with mumps during pregnancy can transmit the infection to their unborn babies, with possible developmental complications.

Because it is a live virus, there has been some concern regarding immunization of pregnant mothers. It is much safer to get all of your recommended immunizations before becoming pregnant.

If you have not been immunized for contagious diseases such as mumps prior to becoming pregnant, it is important to discuss your immunization status with your healthcare provider, and specific recommendations regarding your immunizations during pregnancy will depend on your risk of contracting an illness and the risk to your baby.


There have been mumps outbreaks in which groups of people from the same community develop mumps infection. This has been described among people who were not immunized, as well as among people who were immunized. These outbreaks can occur among people who share living quarters. A number of incidents have been described in college dorms or sports teams, for example. 

Viral Infection From Immunization

Having an immune deficiency may make it difficult for your body to develop immunity in response to any vaccine.

Live vaccines are also sometimes not recommended for people who have a severe immune deficiency. If you have an immune deficiency, you can become infected with the virus at the time of vaccination because your weak immune system cannot adequately fight the virus. This is a very rare occurrence, and you and your healthcare provider will need to discuss the risk of community-acquired infection and the risk of live vaccine infection in your specific case.

Lifestyle Risk Factors

There are a few lifestyle risk factors that increase your chances of becoming infected with mumps.

Not Being Vaccinated

If you have not been vaccinated, this puts you at a high risk of becoming infected with mumps. There has been a re-emergence of the infection, which is largely seen as a result of unvaccinated exposure.

Sharing Space With Someone Who Isn't Vaccinated

It would be very difficult for you to be able to know who could potentially expose you or your child to mumps, especially if you do not know their medical history. Often, there are local or institutional regulations about vaccination when it comes to participation in group activities, such as school trips.

However, situations in which large groups of people stay together and share objects that could contain respiratory droplets increase the chances of exposure to all types of bacterial and viral infections, including mumps. In all cases, do your best to practice proper hygiene. Hand washing and disinfecting, a simple act, can help.

Frequently Asked Questions

  • How do you catch mumps?

    People who are infected can pass on the virus that causes mumps by sneezing or coughing. They may also leave germs on surfaces. If you touch the surface and then touch your nose, eyes, or mouth, the virus can enter your body. 

  • How long are you contagious when you have mumps?

    You’re contagious for about two to three weeks before you have symptoms. Then you’re contagious for about nine days after your parotid or submandibular glands start to swell. Stay home and avoid interacting with others during that period.

  • Can I get mumps if I’m fully vaccinated?

    Yes, but it’s unlikely. The two-dose vaccine is 88% effective against the virus, and outbreaks of mumps are very rare in the United States to begin with, so chances are low. However, some people don’t achieve full immunity with the vaccine and may develop a minor case of mumps if they’re exposed.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Mumps Vaccination | CDC. Centers for Disease Control and Prevention.

  3. Arvas A. Vaccination in patients with immunosuppression. Turk Pediatri Ars. 2014;49(3):181-5. doi:10.5152/tpa.2014.2206

  4. Lozo S, Ahmed A, Chapnick E, O'keefe M, Minkoff H. Presumed cases of mumps in pregnancy: clinical and infection control implications. Infect Dis Obstet Gynecol. 2012;2012:345068. doi:10.1155/2012/345068

  5. Centers for Disease Control and Prevention. Outbreak-related questions and answers for patients.

  6. Cleveland Clinic. Mumps.

Additional Reading

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.