Mumps Cases Rising: Symptoms, Vaccine & Prevention Guide

Is mumps making a quiet return? While much of the public health conversation centers on the ongoing measles outbreaks – including a significant one in South Carolina with nearly 1,000 cases – health officials are also tracking a rise in mumps cases across the country. By the end of February 2026, the Centers for Disease Control and Prevention had identified 34 mumps cases this year, a notable increase compared to previous years. This uptick serves as a reminder that even with highly effective vaccines, infectious diseases remain a persistent threat, particularly in settings where close contact is common.

A Shift in the Landscape of Vaccine-Preventable Illnesses

The recent increase in mumps cases is particularly noticeable in Maryland, which has reported 19 confirmed and 7 probable cases as of late February 2026. This contrasts sharply with the 4 reported cases for all of 2025. Although 34 cases nationally is still a relatively low number, experts emphasize the importance of vigilance and maintaining high vaccination rates. The virus thrives in environments where people are in close proximity for extended periods, such as schools and college campuses.

Vaccination rates against mumps, delivered through the MMR (measles, mumps, and rubella) vaccine, are below the estimated 90 percent herd immunity threshold in some areas of the United States. This lower level of immunity creates opportunities for the virus to spread more easily. Before the introduction of the MMR vaccine in 1967, mumps was a common childhood illness. The vaccine dramatically reduced the incidence of the disease, from approximately 150,000 cases in 1968 to around 230 in 2003.

Understanding Vaccine Effectiveness and Waning Immunity

While mumps isn’t as contagious as measles, the MMR vaccine is less effective against mumps than it is against measles. Here’s a key reason why achieving and maintaining high herd immunity is so crucial. According to Dr. Christy Beneri, the assistant medical director of infection prevention and control at Stony Brook Children’s Hospital in New York, one dose of the MMR vaccine is about 72 percent effective, while two doses offer approximately 86 percent protection.

This means that even vaccinated individuals can still contract mumps, a phenomenon known as a breakthrough infection. Immunity from the vaccine can wane over time, potentially contributing to cases in older adolescents and adults. Dr. Yvonne Maldonado, a professor of pediatrics and infectious diseases at Stanford University, suggests that the current cases in the U.S. Are likely a result of both undervaccination and the imperfect, and sometimes decreasing, effectiveness of the vaccine.

Recognizing the Symptoms of Mumps

Mumps primarily affects the salivary glands, leading to pain and swelling, particularly in the parotid gland near the jaw. The most recognizable symptom is puffiness along the jawline. However, other symptoms can include fever, headache, muscle aches, fatigue, and loss of appetite. Teens and adults are generally more likely to experience noticeable symptoms compared to young children.

How Mumps Spreads and Its Potential Severity

The mumps virus spreads through saliva and respiratory secretions when an infected person coughs, sneezes, talks, or shares drinks or utensils. Importantly, individuals can be contagious for up to two days *before* the characteristic swelling of the salivary glands appears, making it challenging to prevent transmission. Some people may experience mild illness or even no symptoms at all, yet still be able to spread the virus.

Most people who contract mumps recover with bed rest, fluids, and supportive care, without experiencing long-term health problems. However, complications can occur, particularly in unvaccinated individuals, adults, and those with weakened immune systems. A common complication is orchitis, or inflammation of the testicles, which can potentially affect fertility. Other, less frequent complications include meningitis (inflammation of the membranes surrounding the brain and spinal cord), encephalitis (inflammation of the brain), inflammation of the pancreas, and hearing loss. Learn more about meningitis here.

Vaccination: The Primary Defense Against Mumps

The most effective way to protect against mumps is through vaccination. The American Academy of Pediatrics recommends two doses of the MMR or MMRV (measles, mumps, rubella, and varicella) vaccine: the first between 12 and 15 months of age, and the second between 4 and 6 years.

While additional booster doses are not routinely recommended, public health authorities may suggest an extra dose during outbreaks for those at increased risk of exposure. If you are unsure of your vaccination status, it’s advisable to consult with your healthcare provider and review your records. A blood test can determine if you have protective antibodies from past immunization.

Practical Steps to Limit Transmission

Beyond vaccination, several practical steps can support reduce the spread of mumps. These include avoiding sharing drinks or utensils, practicing frequent handwashing, and staying home if you develop symptoms. The South Carolina Department of Public Health provides resources on infectious disease prevention.

Ongoing Surveillance and Future Guidance

Public health agencies continue to monitor mumps cases closely through ongoing surveillance systems. This data informs recommendations regarding vaccination and outbreak response. The CDC regularly updates its guidance based on the latest scientific evidence and epidemiological trends. It’s important to stay informed about official public health updates and consult with a qualified healthcare professional for personalized advice.

The current situation with mumps, alongside the ongoing measles outbreaks, underscores the importance of maintaining strong immunization programs and remaining vigilant against vaccine-preventable diseases. The CDC’s measles data and research page provides the latest information on measles cases and outbreaks in the United States.