Mumps is a contagious viral infection that causes painful swelling of the salivary glands, creating the characteristic “chipmunk cheeks” appearance that many recognize as the hallmark of this disease. While once a common childhood illness, mumps has become much less frequent thanks to widespread vaccination programs, though outbreaks still occur in certain settings where people live or work in close contact with one another.

Understanding Mumps: A Global Health Perspective

Mumps remains an important public health concern around the world, even though vaccination has dramatically reduced its impact in many countries. The disease is caused by the mumps virus, which belongs to a family of viruses known as paramyxoviruses—microscopic infectious agents that contain genetic material wrapped in a protein coat.^[1] This virus specifically targets the salivary glands, particularly the parotid glands located between the ear and jaw, causing them to swell and become tender.

Before the introduction of the mumps vaccine in 1967, the disease was extremely common in the United States, with approximately 186,000 cases reported each year.^[12] The impact of vaccination has been remarkable—there has been more than a 99% decrease in mumps cases since the vaccination program began.^[1] However, the virus has not been eliminated entirely. Mumps continues to circulate globally and remains endemic in many countries, meaning it is consistently present in certain populations.

The disease most commonly affects children between the ages of 2 and 12 who have not received the mumps vaccine.^[3] However, adolescents and adults can also contract mumps, sometimes even after being vaccinated. This occurs because the protection provided by the vaccine can weaken over time, a phenomenon known as waning immunity.^[3] In recent years, outbreaks have been particularly noted on college campuses and in other settings where people have prolonged close contact with one another.

The Root Causes of Mumps

Mumps is caused exclusively by infection with the mumps virus. This single-stranded RNA virus is the only known cause of epidemic parotitis, which is the medical term for widespread inflammation of the parotid salivary glands.^[8] The virus has been classified into 12 different genotypes, with genotype G being the primary strain circulating in the United States since 2006.^[8]

The virus is highly contagious and spreads easily from person to person through several routes. When an infected person coughs, sneezes, or talks, they release tiny droplets containing the virus into the air. These respiratory droplets can be inhaled by people nearby, leading to infection.^[1] Additionally, the virus can spread through direct contact with saliva. This means sharing drinking glasses, water bottles, eating utensils, or even kissing someone who is infected can transmit the disease.

The virus can also survive on surfaces contaminated with infected saliva. When someone touches these surfaces and then touches their eyes, nose, or mouth, they can become infected.^[1] Participating in close-contact activities such as playing sports, dancing, or simply being in crowded spaces increases the risk of transmission.

What makes mumps particularly challenging to control is its contagious period. An infected person can spread the virus to others starting a few days before their salivary glands begin to swell and continuing until up to five days after the swelling begins.^[1] The person is most contagious approximately 48 hours before symptoms appear.^[4] This means people can unknowingly spread the disease before they even realize they are sick.

Who Is at Risk for Mumps?

Anyone who lacks immunity to the mumps virus is at risk of contracting the disease. Immunity typically comes from either previous infection with mumps or from vaccination. However, certain groups of people face higher risks than others.

People who have never been vaccinated against mumps are at the highest risk of infection.^[3] This includes individuals who may have missed their childhood vaccinations or who live in areas where vaccination programs are not widely available. Children under one year of age are generally protected by antibodies they receive from their mothers during pregnancy, but this protection fades over time.^[6]

Individuals who live or work in crowded or close-knit settings are more likely to be exposed to the virus. School-aged children, college students living in dormitories, and healthcare workers all face increased risk.^[1] People who travel internationally, especially to areas where mumps is still common, also have a higher likelihood of encountering the virus.

Those with weakened immune systems, whether from disease or medication, may be more susceptible to infection and potentially more likely to develop complications.^[3] Additionally, people born before 1957 are generally considered immune because they likely were exposed to the virus naturally during childhood when mumps was widespread.^[7]

Recognizing the Symptoms of Mumps

Mumps does not cause symptoms immediately after infection. There is an incubation period—the time between when the virus enters the body and when symptoms appear—that typically ranges from 16 to 18 days, though it can be as short as 12 days or as long as 25 days.^[7] During this time, infected individuals may feel perfectly fine but can still spread the virus to others.

The initial symptoms of mumps are often mild and non-specific, resembling those of a common cold or flu. People typically experience a low-grade fever, headache, muscle aches, fatigue, and loss of appetite.^[2] Some may feel generally unwell without being able to pinpoint exactly what is wrong. These early symptoms usually begin a few days before the characteristic swelling appears.

The hallmark symptom of mumps is painful swelling of the salivary glands, particularly the parotid glands located between the ears and jaw. This swelling, called parotitis, causes the cheeks to puff out and the jaw to swell, creating the distinctive “chipmunk cheeks” appearance that is so closely associated with mumps.^[3] The swelling typically begins on one side of the face and may spread to the other side after a day or two, though sometimes only one side is affected.

The swollen glands are not just unsightly—they are quite painful and tender to the touch. The skin over the swollen area appears stretched and shiny but is not usually red.^[15] The pain intensifies when the person chews, swallows, talks, or drinks acidic beverages like orange juice.^[1] Some people experience earache or find it difficult to speak clearly due to the swelling.

Interestingly, not everyone infected with the mumps virus develops these classic symptoms. Approximately one-third of infected individuals have no symptoms at all and may never know they had mumps.^[6] Others may experience only mild symptoms that they might mistake for a regular cold. This makes it difficult to control the spread of the disease, as asymptomatic individuals can still transmit the virus to others.

Most people with mumps recover completely within two weeks, with the swelling typically subsiding within five to seven days.^[15] However, in some cases, mumps can affect other parts of the body beyond the salivary glands, leading to more serious complications.

Complications: When Mumps Becomes Serious

While mumps is usually a mild, self-limiting disease, it can sometimes cause serious complications, particularly in adolescents and adults. These complications can occur with or without the characteristic parotitis, making them sometimes difficult to recognize as mumps-related.

One of the most common complications in males who have reached puberty is orchitis, which is inflammation of the testicles. This occurs in approximately 10% of post-pubescent males who contract mumps.^[16] Orchitis causes painful swelling of one or both testicles, typically appearing four to eight days after the parotid swelling begins. While uncomfortable and concerning, orchitis rarely leads to infertility, though it may occasionally cause a decrease in testicular size.^[7]

In females who have reached puberty, mumps can cause oophoritis, which is inflammation of the ovaries, though this occurs less frequently than orchitis in males. Some women may also experience inflammation of breast tissue.^[7] Neither orchitis nor oophoritis caused by mumps has been shown to lead to infertility, contrary to common fears.^[12]

Pancreatitis, or inflammation of the pancreas, is another possible complication. This causes severe stomach pain and may be accompanied by nausea and vomiting.^[7] The inflammation typically resolves as the mumps infection clears, but it can be quite uncomfortable while it lasts.

Perhaps the most concerning complications involve the nervous system. Meningitis, which is inflammation of the membranes covering the brain and spinal cord, can occur in up to one-fourth of people with mumps.^[6] Symptoms include severe headache, stiff neck, sensitivity to bright light, confusion, and vomiting. More rarely, mumps can cause encephalitis, which is inflammation of the brain itself. This is a medical emergency and requires immediate attention.

Temporary or, rarely, permanent hearing loss can result from mumps infection. This typically affects only one ear and can range from mild to complete deafness.^[5] Other rare complications include inflammation of the kidneys or heart muscle.^[7]

It is important to note that vaccinated individuals who contract mumps are less likely to develop these serious complications compared to those who are unvaccinated.^[7] This is one of the many reasons why vaccination remains so important even though breakthrough infections can occur.

Preventing Mumps Through Vaccination

Vaccination is by far the most effective way to prevent mumps. The mumps vaccine is typically given as part of the MMR vaccine, which protects against measles, mumps, and rubella all in one shot. Some children may receive the MMRV vaccine, which also includes protection against varicella (chickenpox).^[1]

The standard vaccination schedule recommends that children receive their first dose of MMR vaccine between 12 and 15 months of age, ideally as soon as possible within this window. The second dose is typically administered between four and six years of age, though it can be given as early as one month after the first dose.^[7] These two doses provide long-term protection against mumps for most people.

Certain groups are considered at higher risk for mumps and may need to ensure they have received two doses of the vaccine. These include college students, healthcare workers, and international travelers.^[7] If you are unsure whether you have been properly vaccinated, you can check with your healthcare provider or, in some cases, have a blood test to determine your immunity status.

During mumps outbreaks, some healthcare providers may recommend a third dose of the MMR vaccine for people who are at particularly high risk of exposure. However, a third dose is not currently part of routine vaccination recommendations and is not required by law for school attendance.^[22]

People born before 1957 are generally considered immune to mumps because they likely encountered the virus naturally when it was widespread. They typically do not need vaccination unless they are healthcare workers or have other specific risk factors.^[7]

Beyond vaccination, several practical measures can help reduce the spread of mumps. Regular handwashing with soap and water is crucial, especially after being in public spaces or around people who are sick.^[1] Avoid sharing eating utensils, drinking glasses, water bottles, or other items that may come into contact with saliva. Cover your mouth and nose with a tissue when coughing or sneezing, and dispose of tissues properly.

If you know you have been exposed to someone with mumps and have not been fully vaccinated, contact your healthcare provider immediately. You may need to stay home from work or school during the incubation period to prevent potentially spreading the disease to others.^[7]

There has been concern among some parents about a possible link between the MMR vaccine and autism spectrum disorder. However, extensive scientific research involving many studies has found no connection between vaccines and autism.^[9] The benefits of vaccination in preventing serious diseases far outweigh any potential risks.

How Mumps Affects the Body

Understanding what happens inside the body during a mumps infection helps explain why the disease causes the symptoms it does and why certain complications can occur. The journey of the mumps virus through the body follows a predictable pattern.

When the mumps virus enters the body, usually through the nose or mouth, it first infects the cells lining the upper respiratory tract. The virus begins multiplying in these cells, establishing its initial foothold in the body. From there, it spreads to nearby lymph nodes, which are small organs that are part of the immune system.

Once the virus has replicated sufficiently in the lymph nodes, it enters the bloodstream. This phase, called viremia, allows the virus to travel throughout the entire body via the blood.^[6] This is why mumps can potentially affect multiple organs and tissues beyond just the salivary glands.

The virus has a particular affinity for glandular and nervous tissue. The parotid salivary glands are the most commonly affected organs. When the virus infects these glands, it triggers an inflammatory response. The body’s immune system recognizes the virus as foreign and sends white blood cells to fight the infection. This immune response causes the glands to swell with fluid and become painful—the characteristic parotitis that defines mumps.

The parotid glands are not the only salivary glands that can be affected. The submandibular glands beneath the floor of the mouth and the sublingual glands under the tongue may also become inflamed, though less commonly.^[2]

When complications occur, it is because the virus has infected other organs. If the virus reaches the testicles, ovaries, or pancreas, it causes inflammation in these organs through the same immune response mechanism. When the virus crosses into the central nervous system, it can infect the membranes surrounding the brain and spinal cord (causing meningitis) or the brain tissue itself (causing encephalitis).

The inner ear structures, particularly those responsible for hearing, can also be affected by the virus. Inflammation in these delicate structures can lead to temporary or permanent hearing damage. The exact mechanism by which mumps causes hearing loss is not fully understood but likely involves both direct viral damage to hearing cells and inflammation-related injury.

Throughout the infection, the immune system is working to eliminate the virus from the body. It produces antibodies—specialized proteins that recognize and neutralize the virus. Once the infection is cleared, these antibodies typically remain in the bloodstream for life, providing immunity against future mumps infections. This is why most people who have had mumps once will not get it again.

The entire course of infection, from initial viral replication to complete clearance by the immune system, usually takes about two weeks. The body’s ability to successfully fight off the virus and recover completely is why mumps is generally considered a self-limiting disease that does not require specific antiviral treatment.