Mumps is a contagious viral infection best known for causing puffy, swollen cheeks and jaw. The virus targets the salivary glands, particularly the parotid glands that sit just below and in front of your ears, giving infected people a distinctive “chipmunk cheek” appearance. Thanks to widespread vaccination, mumps is far less common than it once was, but outbreaks still happen, and understanding the infection matters whether you’re a parent, a college student, or just curious.
What Causes Mumps
Mumps is caused by a virus in the paramyxovirus family, the same broad family that includes parainfluenza viruses. The virus is wrapped in a fatty envelope studded with proteins that latch onto the surface of human cells. Once attached, the virus fuses with the cell membrane, slips inside, and hijacks the cell’s machinery to copy itself. New virus particles then bud off the cell surface and spread to infect neighboring tissue.
The virus spreads from person to person through respiratory droplets and saliva. Coughing, sneezing, sharing utensils, or close conversation can all pass it along. A person with mumps is contagious from about 2 days before the swelling starts until 5 days after, though the virus has been detected in saliva as early as 7 days before symptoms and up to 9 days after. The incubation period, the gap between catching the virus and feeling sick, averages 16 to 18 days but can range from 12 to 25.
How Mumps Feels
The first signs are vague and easy to mistake for any mild illness: low-grade fever, muscle aches, loss of appetite, fatigue, and headache. These can last 3 to 4 days before the hallmark swelling begins.
Then one or both parotid glands swell up. The swelling is painful and tender, and it can be dramatic enough to hide the angle of the jawbone entirely. In about 25% of cases, only one side swells. Sometimes one gland puffs up first and the other follows a day or two later. The swelling typically lasts around 5 days, with most cases fully resolving within 10 days. Some people infected with mumps never develop noticeable swelling at all, which makes the virus tricky to track during outbreaks.
Possible Complications
Most people recover from mumps without lasting problems, but the virus can affect organs beyond the salivary glands. Complications can occur even in people who never develop the classic cheek swelling.
The most common complication in males past puberty is orchitis, painful swelling of one or both testicles. Among unvaccinated men, roughly 30% develop orchitis; among vaccinated men, the rate drops to about 6%. Orchitis rarely causes complete sterility, but it can reduce fertility. An estimated 13% of men with orchitis experience some degree of impaired fertility afterward, and the risk climbs significantly when both testicles are affected.
In women past puberty, the virus can cause ovarian inflammation (reported in about 7% of unvaccinated cases) or breast tissue inflammation (up to 30% in the pre-vaccine era). Both are now rare among vaccinated women, occurring in 1% or fewer of cases.
Before vaccines were available, up to 10% of unvaccinated mumps patients developed viral meningitis, an inflammation of the membranes surrounding the brain and spinal cord. Pancreatitis and hearing loss each occurred in up to 4% of cases. Hearing loss is usually temporary but can become permanent. In the vaccine era, meningitis, encephalitis, pancreatitis, and hearing loss each occur in 1% or fewer of all mumps infections.
How It’s Diagnosed
Doctors often suspect mumps based on the telltale parotid swelling, especially during a known outbreak. But because other viruses can cause similar symptoms, lab testing confirms the diagnosis. The standard test uses a buccal swab, a soft swab rubbed along the inside of the cheek near the parotid gland duct, to detect viral genetic material.
Timing matters. If you’re within the first 3 days of symptoms, a swab alone is usually enough. After 3 days, doctors typically collect both a swab and a blood sample to look for antibodies the immune system produces in response to the virus. If complications like orchitis, meningitis, or hearing loss are present, both tests are collected regardless of timing.
Treatment and Recovery
There is no antiviral medication that targets mumps. Treatment focuses entirely on managing symptoms while your immune system clears the virus. That means rest, plenty of fluids, and over-the-counter pain relievers like ibuprofen or acetaminophen to reduce fever and ease the aching.
A warm or cool cloth pressed against swollen glands can help with discomfort. If orchitis develops, a cold cloth or ice pack on the affected area provides some relief. Soft foods are easier to chew when your jaw is swollen and tender. Acidic or tart foods and drinks (orange juice, lemonade) can make the pain worse because they stimulate saliva production in already-inflamed glands. Most people feel significantly better within two weeks.
How Vaccination Protects You
The mumps vaccine is given as part of the MMR (measles, mumps, rubella) combination vaccine. The CDC recommends the first dose between 12 and 15 months of age and the second dose between ages 4 and 6. One dose provides about 72% protection against mumps. Two doses raise that to about 86%.
That 86% effectiveness is lower than what the MMR achieves against measles (around 97%), which is one reason mumps outbreaks still pop up, particularly in settings where people are in close, prolonged contact: college dorms, sports teams, and close-knit communities. Immunity also appears to fade over time. During outbreaks, public health authorities sometimes recommend a third dose of MMR for people who are at increased risk, even if they’ve already had two doses.
Vaccinated people who do catch mumps tend to have milder symptoms and far fewer complications. The steep drop in orchitis, meningitis, and hearing loss rates in the vaccine era reflects not just fewer infections overall but less severe disease when breakthrough infections occur.