Our Vaccine Update feature article “Fast Facts” series continues this month with a look at mumps. Much of the focus on declining rates of MMR vaccination has been on the increase in measles outbreaks, which have plagued the country since January 2025. Yet with declining MMR rates, attention should be paid to the second “M” in the vaccine: Mumps.
As of August 2025, 205 cases of mumps had been confirmed in the U.S. As recently as 2016 and 2017, more than 6,000 cases were identified each year. Reassuringly, these figures remain far below the approximately 150,000 cases that occurred annually in the U.S. before a mumps vaccine was available. But the rarity of this disease now makes it more challenging to recognize.
Recognizing mumps
Mumps is a virus that causes inflammation and swelling of salivary glands — most specifically, the parotid glands. Parotitis can be on one or both sides of the face and is often accompanied by other typical symptoms of a viral infection, like fatigue, decreased appetite, muscle aches, headache, and low-grade fever. The illness typically lasts between seven and 10 days.
While most mumps infections are mild, certain manifestations are severe, and it is these outcomes that drove national efforts to institute universal vaccination. Three manifestations were of particular concern.
- Meningitis: Mumps used to be the most common cause of meningitis in children.
- Hearing loss: One of every 20,000 people infected with mumps were left with permanent hearing loss. In fact, mumps was the leading cause of deafness prior to the availability of a vaccine.
- Sterility: Both males and females can become sterile after a mumps infection. Mumps can infect the testicles, leading to orchitis. This occurs in 1 of every 3 unvaccinated males who have completed puberty when their infection occurs. In females, mumps can infect the ovaries, leading to oophoritis.
In rare cases, patients can experience inflammation of the heart or pancreas. Finally, if a woman gets mumps during pregnancy, the infant may be stillborn.
Making a mumps diagnosis
Mumps should be considered if a patient presents with the aforementioned clinical presentations. It can be diagnosed through laboratory testing. Buccal swabs for PCR-based tests are preferred over serology whenever possible. This is for two reasons. First, with molecular based testing, the virus can be characterized to help with ongoing analysis of circulating mumps virus. Second, serologic testing is more challenging to interpret. IgM tests may not be positive in a previously vaccinated person, or they may be falsely positive as this test cross-reacts with other viruses. During outbreaks, local public health officials may provide localized guidance to optimize testing resources.
All cases of mumps need to be reported to health departments for ongoing surveillance.
Treatment and management of mumps
No specific treatments for mumps exist; however, patients can benefit from supportive care. Individuals with more severe manifestations, such as meningitis, may require hospitalization.
Because of the contagious nature of mumps, infected individuals should isolate for five days after the onset of parotid swelling. For patients with lab-confirmed mumps without parotid swelling, they should isolate for five days from the onset of their first symptom, whether that is a non-specific respiratory symptom or a more specific presentation, like orchitis.
Long-term impacts
Deafness from mumps may be temporary, but about 1 of every 20,000 people infected will be permanently deaf. When unvaccinated males who have gone through puberty are infected, about 1 of every 3 will have orchitis, resulting in decreased fertility. For some, this will lead to complete sterility.
Infection control: Reducing the spread of mumps
Mumps is spread through respiratory secretions, including coughing and sneezing. Kissing; sharing contaminated objects, like water bottles or utensils; or having a close conversation with an infected person can also spread the virus. People are most contagious during the two days before the onset of swollen glands. Symptoms typically begin between 12 and 25 days after exposure. Some patients may be asymptomatic, making outbreak dynamics challenging to understand.
Mumps outbreaks tend to occur in settings where people have prolonged, close contact, such as in universities, schools and correctional facilities. Notably, previously vaccinated people can still be infected. There are a few potential reasons for this:
- The individual’s initial immune response to the vaccine was insufficient.
- Circulating antibodies decline over time.
- Currently circulating strains are antigenically different from the vaccine strain.
- High vaccination rates and low levels of viral circulation in the community have led to fewer natural opportunities for immunologic boosting.
During outbreaks, public health authorities may recommend a third dose of vaccine to people in high-risk groups. For example, if there is an outbreak on a college campus, people in a specific dorm or on a specific sports team may be recommended to get a third dose. Vaccinating already exposed individuals who were previously unvaccinated will not change their risk for infection, but they should complete the recommended vaccination series for protection against future exposures.
Mumps: Key clinical takeaways
Mumps remains uncommon, though outbreaks in crowded settings occur. If rates of MMR vaccination continue to erode, mumps outbreaks may become more widespread, and we may begin to see them in currently uncommon settings, such as child care centers. Providers should be prepared to recognize and test for mumps, as well as provide counsel to families about all three of the illnesses that MMR vaccine prevents.
Resources for families
- Measles, Mumps and Rubella (MMR): The Diseases & Vaccines (webpage)
- MMR infographic: English | Spanish
- Vaccines on the Go: What You Should Know (mobile app)
Resources for providers
Our Vaccine Update feature article “Fast Facts” series continues this month with a look at mumps. Much of the focus on declining rates of MMR vaccination has been on the increase in measles outbreaks, which have plagued the country since January 2025. Yet with declining MMR rates, attention should be paid to the second “M” in the vaccine: Mumps.
As of August 2025, 205 cases of mumps had been confirmed in the U.S. As recently as 2016 and 2017, more than 6,000 cases were identified each year. Reassuringly, these figures remain far below the approximately 150,000 cases that occurred annually in the U.S. before a mumps vaccine was available. But the rarity of this disease now makes it more challenging to recognize.
Recognizing mumps
Mumps is a virus that causes inflammation and swelling of salivary glands — most specifically, the parotid glands. Parotitis can be on one or both sides of the face and is often accompanied by other typical symptoms of a viral infection, like fatigue, decreased appetite, muscle aches, headache, and low-grade fever. The illness typically lasts between seven and 10 days.
While most mumps infections are mild, certain manifestations are severe, and it is these outcomes that drove national efforts to institute universal vaccination. Three manifestations were of particular concern.
- Meningitis: Mumps used to be the most common cause of meningitis in children.
- Hearing loss: One of every 20,000 people infected with mumps were left with permanent hearing loss. In fact, mumps was the leading cause of deafness prior to the availability of a vaccine.
- Sterility: Both males and females can become sterile after a mumps infection. Mumps can infect the testicles, leading to orchitis. This occurs in 1 of every 3 unvaccinated males who have completed puberty when their infection occurs. In females, mumps can infect the ovaries, leading to oophoritis.
In rare cases, patients can experience inflammation of the heart or pancreas. Finally, if a woman gets mumps during pregnancy, the infant may be stillborn.
Making a mumps diagnosis
Mumps should be considered if a patient presents with the aforementioned clinical presentations. It can be diagnosed through laboratory testing. Buccal swabs for PCR-based tests are preferred over serology whenever possible. This is for two reasons. First, with molecular based testing, the virus can be characterized to help with ongoing analysis of circulating mumps virus. Second, serologic testing is more challenging to interpret. IgM tests may not be positive in a previously vaccinated person, or they may be falsely positive as this test cross-reacts with other viruses. During outbreaks, local public health officials may provide localized guidance to optimize testing resources.
All cases of mumps need to be reported to health departments for ongoing surveillance.
Treatment and management of mumps
No specific treatments for mumps exist; however, patients can benefit from supportive care. Individuals with more severe manifestations, such as meningitis, may require hospitalization.
Because of the contagious nature of mumps, infected individuals should isolate for five days after the onset of parotid swelling. For patients with lab-confirmed mumps without parotid swelling, they should isolate for five days from the onset of their first symptom, whether that is a non-specific respiratory symptom or a more specific presentation, like orchitis.
Long-term impacts
Deafness from mumps may be temporary, but about 1 of every 20,000 people infected will be permanently deaf. When unvaccinated males who have gone through puberty are infected, about 1 of every 3 will have orchitis, resulting in decreased fertility. For some, this will lead to complete sterility.
Infection control: Reducing the spread of mumps
Mumps is spread through respiratory secretions, including coughing and sneezing. Kissing; sharing contaminated objects, like water bottles or utensils; or having a close conversation with an infected person can also spread the virus. People are most contagious during the two days before the onset of swollen glands. Symptoms typically begin between 12 and 25 days after exposure. Some patients may be asymptomatic, making outbreak dynamics challenging to understand.
Mumps outbreaks tend to occur in settings where people have prolonged, close contact, such as in universities, schools and correctional facilities. Notably, previously vaccinated people can still be infected. There are a few potential reasons for this:
- The individual’s initial immune response to the vaccine was insufficient.
- Circulating antibodies decline over time.
- Currently circulating strains are antigenically different from the vaccine strain.
- High vaccination rates and low levels of viral circulation in the community have led to fewer natural opportunities for immunologic boosting.
During outbreaks, public health authorities may recommend a third dose of vaccine to people in high-risk groups. For example, if there is an outbreak on a college campus, people in a specific dorm or on a specific sports team may be recommended to get a third dose. Vaccinating already exposed individuals who were previously unvaccinated will not change their risk for infection, but they should complete the recommended vaccination series for protection against future exposures.
Mumps: Key clinical takeaways
Mumps remains uncommon, though outbreaks in crowded settings occur. If rates of MMR vaccination continue to erode, mumps outbreaks may become more widespread, and we may begin to see them in currently uncommon settings, such as child care centers. Providers should be prepared to recognize and test for mumps, as well as provide counsel to families about all three of the illnesses that MMR vaccine prevents.
Resources for families
- Measles, Mumps and Rubella (MMR): The Diseases & Vaccines (webpage)
- MMR infographic: English | Spanish
- Vaccines on the Go: What You Should Know (mobile app)