While measles is making headlines in the United States, with an ongoing South Carolina outbreak reaching almost 1,000 cases, public health experts are on the lookout for another vaccine-preventable infectious disease: mumps.
By the end of February 2026, the Centers for Disease Control and Prevention had identified 34 mumps cases this year. That included 19 confirmed cases and 7 probable cases in Maryland, a notable increase compared with 4 reported cases there in all of 2025.
Although 34 is a relatively low number, health experts say it’s a reminder that the mumps virus persists in the United States and can spread — particularly in communities where people spend long periods of time in close contact, such as schools and college campuses.
Why Mumps Still Spreads
In some parts of the United States, the number of people immunized against mumps via inoculations like the MMR (measles, mumps, rubella) vaccine is below the estimated 90 percent herd immunity threshold, making it easier for the virus to spread.
Before the launch of the MMR vaccination program in 1967, most children in the United States got mumps by adolescence. After the program began, reported cases dropped by more than 99 percent — from roughly 150,000 in 1968 to about 230 in 2003.
While mumps is not as contagious as measles, vaccination is less effective against mumps than measles, which is why herd immunity is particularly important.
“One dose of the vaccine is about 72 percent effective, and two doses are about 86 percent effective,” says Christy Beneri, DO, the assistant medical director of infection prevention and control at Stony Brook Children’s Hospital in Stony Brook, New York.
That means some vaccinated people may still develop the illness after exposure, a phenomenon known as breakthrough infection.
“Waning or decreasing immunity is another issue that can contribute to cases appearing in older adolescents and adults,” Dr. Beneri adds.
“Current mumps cases in the U.S. may be the result of a combination of undervaccination in some communities as well as the lower effectiveness of the vaccine,” says Yvonne Maldonado, MD, a professor of pediatrics and infectious diseases at Stanford University in California.
What Are Mumps Symptoms?
Mumps primarily affects the salivary glands. “It typically leads to pain and swelling of the salivary glands, particularly the parotid gland near the jaw,” says Beneri.
The most recognizable symptom is swelling of the parotid glands, which causes puffiness along the jawline.
Other mumps symptoms may include:
Fever
Headache
Muscle aches
Fatigue
Loss of appetite
Teens and adults are more likely than young children to develop noticeable symptoms, Beneri says.
How Does Mumps Spread?
The mumps virus spreads through saliva and respiratory secretions when infected people cough, sneeze, talk, or share drinks or utensils.
People can spread the virus before they realize they are sick. “People are usually contagious for about two days before the swelling of the salivary glands develops,” Beneri says.
Some people develop mild illness or no symptoms at all but can still spread the virus.
How Serious Is Mumps?
Most people who have mumps only require bed rest, plenty of fluids, and other types of supportive care to help with symptoms, and recover without long-term health problems, says Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.
But complications can occur, and are more likely in adults, people who are unvaccinated, and individuals with weakened immune systems, he says.
“The most common complication is orchitis, or inflammation of the testicles, which can lead to testicular atrophy and potentially affect fertility,” Dr. Adalja says.
Other complications include meningitis (inflammation of the membrane surrounding the brain and spinal cord), encephalitis (inflammation of the brain), inflammation of the pancreas, and hearing loss.
Who Should Get the Mumps Vaccine?
The best protection against mumps is vaccination.
The American Academy of Pediatrics recommends that children get two doses of the MMR or the MMRV (measles, mumps, rubella, and varicella) vaccine:
The first dose at 12 to 15 months
The second dose at 4 to 6 years
“In most situations, additional booster doses are not routinely recommended. However, during outbreaks public health authorities may recommend an extra dose for people who are at increased risk of exposure,” says Beneri.
She recommends talking to your healthcare team and reviewing your records if you’re unsure of your vaccination status.
While there is no harm in getting an extra dose, you can also get a blood test to see if you have protective antibodies from past immunization, says Beneri.
How to Protect Yourself and Others From Mumps
Vaccination remains the most effective way to prevent mumps and limit its spread, says Adalja.
Beneri recommends these other practical steps to reduce mumps transmission:
Avoid sharing drinks or utensils.
Wash your hands frequently.
Stay home if you develop symptoms.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Wang D et al. Loss of Protective Immunity of Two-Dose Mumps-Containing Vaccine Over Time: Concerns with the New Strategy of the Mumps Immunization Program in China. Human Vaccines & Immunotherapeutics. February 5, 2021.
Emily Kay Votruba has copy edited and fact-checked for national magazines, websites, and books since 1997, including Self, GQ, Gourmet, Golf Magazine,Outside, Cornell University Press, Penguin Random House, and Harper's Magazine. Her projects have included cookbooks (Padma Lakshmi's Tangy Tart Hot & Sweet), self-help and advice titles (Mika Brzezinski's Know Your Value: Women, Money, and Getting What You're Worth), memoirs (Larry King's My Remarkable Journey), and science (Now You See It: How the Brain Science of Attention Will Transform How We Live, Work, and Learn, by Cathy Davidson). She started freelancing for Everyday Health in 2016.
Becky Upham has worked throughout the health and wellness world for over 25 years. She's been a race director, a team recruiter for the Leukemia and Lymphoma Society, a salesperson for a major pharmaceutical company, a blogger for Moogfest, a communications manager for Mission Health, a fitness instructor, and a health coach.
Upham majored in English at the University of North Carolina and has a master's in English writing from Hollins University.
Upham enjoys teaching cycling classes, running, reading fiction, and making playlists.
