Measles is not the only disease on the rise. Mumps also may be making a comeback

By Katia Hetter, CNN

(CNN) — Measles is not the only vaccine-preventable disease making headlines.

Health officials in Maryland have issued an alert after confirming an uptick in mumps cases — 26 reported so far this year as of February 19, including 19 confirmed and seven probable infections, according to the Maryland Department of Health. Nationally, the US Centers for Disease Control and Prevention reported that as of late February, 11 jurisdictions have documented 34 cases.

Mumps was once a routine childhood illness in the United States before the US Food and Drug Administration approved the first vaccine in 1967 and vaccination dramatically reduced cases. The number of cases in the US decreased from 152,209 in 1968 to 231 in 2003, according to the CDC.

But mumps cases and outbreaks have increased since 2006. So why are outbreaks still occurring — and who should be concerned now?

To help with these and other questions, I turned to CNN wellness expert Dr. Leana Wen, an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner.

CNN: What is mumps, and how is it spread?

Dr. Leana Wen: Mumps is a viral infection caused by the mumps virus, a member of the paramyxovirus family. It primarily affects the salivary glands, especially the parotid glands located just below and in front of the ears. The infection spreads through respiratory droplets and saliva. That means mumps can be transmitted when an infected person coughs, sneezes, talks or shares drinks or utensils.

What makes mumps particularly challenging from a public health standpoint is that people can spread the virus before they realize they are sick. Individuals are generally considered contagious several days before the onset of gland swelling and for about five days afterward. In close-contact settings, such as households, schools, sports teams and college dormitories, transmission can occur relatively quickly.

CNN: What symptoms should people watch for? Is there a difference between how mumps presents in young children versus adolescents and adults?

Wen: The hallmark symptom of mumps is swelling of one or both parotid glands, which can cause puffy cheeks and tenderness along the jaw. This swelling is often accompanied by other nonspecific viral symptoms, including fever, headache, muscle aches, fatigue and loss of appetite. Some people also experience pain when chewing or swallowing.

Symptoms typically develop about two to three weeks after exposure. In children, illness is often mild. Some kids may have only low-grade fever and mild swelling, and others may have no symptoms at all. In fact, a notable percentage of infections in children are asymptomatic or so mild that they go undiagnosed.

Adolescents and adults are more likely to experience more pronounced symptoms and complications. Swelling may be more painful, fevers may be higher and systemic symptoms such as fatigue can be more significant. This age-related difference is one reason why outbreaks in middle schools, high schools and colleges receive particular attention.

CNN: What are the most serious complications, and who is at highest risk?

Wen: While many cases resolve without lasting problems, mumps can lead to serious complications. One of the most well-known is orchitis, or inflammation of the testicles. Orchitis can be quite painful and, in rare instances, may lead to reduced fertility.

Females can develop oophoritis, which is inflammation of the ovaries, and/or mastitis, which is inflammation of breast tissue. Though these conditions are uncomfortable, they are less commonly associated with long-term consequences.

Mumps also can affect the central nervous system. Meningitis, or inflammation of the lining around the brain and spinal cord, occurs in a small percentage of cases. Encephalitis, or inflammation of the brain itself, is rare but potentially life-threatening. Permanent hearing loss is another rare but serious complication. People who are unvaccinated are at the highest risk of both infection and complications.

CNN: If someone is diagnosed with mumps, what treatment is available, and how long are they contagious?

Wen: There is no specific antiviral medication that targets the mumps virus. Treatment is supportive, meaning it focuses on relieving symptoms while the body clears the infection. This includes rest, staying well-hydrated and using over-the-counter pain relievers such as acetaminophen or ibuprofen to reduce fever and discomfort. Warm or cold compresses may help ease gland swelling.

Because mumps is contagious, isolation is important. Individuals diagnosed with mumps are advised to stay home and avoid contact with others for five days after their symptoms appear. This precaution reduces the risk of spreading the virus in schools, workplaces and other community settings.

If someone develops severe headache, stiff neck, confusion, persistent vomiting, severe abdominal pain or testicular pain, they should seek medical care promptly as these may signal complications requiring further evaluation.

CNN: How effective is the measles, mumps and rubella vaccine against mumps, and why can outbreaks still happen in vaccinated communities?

Wen: The MMR vaccine is highly effective at preventing mumps, though it is somewhat less protective against mumps than against measles or rubella. Two doses of MMR are estimated to be about 86% effective at preventing mumps infection; one dose is about 72% effective. Children are recommended to receive two doses of the MMR vaccine, the first at between 12 and 15 months old and the second at 4 to 6 years old.

No vaccine is 100% effective, which means that some vaccinated individuals can still become infected. This phenomenon is known as breakthrough infection. In most cases, breakthrough infections are milder and less likely to result in complications.

Outbreaks can occur in settings where people are in close contact for prolonged periods, even when overall vaccination coverage is high. Colleges are a classic example. If immunity wanes over time — which appears to occur with mumps to some extent — individuals vaccinated in early childhood may have reduced protection as young adults. When the virus is introduced into a tightly connected community, it can spread among susceptible individuals.

Importantly, outbreaks are far more limited and less severe than they would be without vaccination. High community vaccination rates help contain spread and protect people who cannot be vaccinated, such as young babies or individuals with certain medical conditions.

CNN: How can adults tell whether they are adequately protected, and who would benefit from an additional dose during an outbreak?

Wen: In general, people born before 1957 are presumed to have immunity given how prevalent mumps was before this time. Those folks born in or after this time should have documentation of vaccination. Adults who are unsure can check vaccination records or consult with their health care provider. In some cases, a blood test can assess immunity.

Certain groups are considered at higher risk and should ensure they are fully vaccinated, such as college students, health care personnel, international travelers and others who may be exposed in close-contact environments.

During a mumps outbreak, public health authorities may recommend a third dose of MMR for people identified as being at increased risk because of their exposure. This additional dose is intended to boost immunity in the short term and help control the outbreak. This step is not a routine recommendation for the general population but is used strategically when clusters occur.

For individuals who lack documentation and have no contraindications, receiving the MMR vaccine is safe and effective. The vaccine has been used for decades and has a well-established safety profile. Staying up to date not only protects the individual but also contributes to broader community protection.

As recent reports show, mumps has not vanished. Even relatively small increases in cases serve as a reminder that vaccination and timely public health response remain essential in keeping preventable diseases at bay.

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