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From the Merck Manual Consumer Version, edited by Robert Porter. Copyright 2015 by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co, Inc, Kenilworth, NJ. Available at merckmanuals.com. Accessed June 2015.
Mumps is a viral illness caused by a paramyxovirus, a member of the Rubulavirus family. The average incubation period for mumps is 16 to 18 days, with a range of 12 to 25 days.
Mumps usually involves pain, tenderness, and swelling in one or both parotid salivary glands (cheek and jaw area). Swelling is first visible in front of the lower part of the ear. It then extends downward and forward as fluid builds up in the skin and soft tissue of the face and neck. Swelling usually peaks in 1 to 3 days and then subsides during the next week. The swollen tissue pushes the angle of the ear up and out. As swelling worsens, the angle of the jawbone below the ear is no longer visible. Often, the jawbone cannot be felt because of swelling of the parotid. One parotid may swell before the other, and in 25% of patients, only one side swells. Other salivary glands (submandibular and sublingual) under the floor of the mouth also may swell but do so less frequently (10%).
Nonspecific prodromal symptoms may precede parotitis by several days, including low-grade fever which may last three to four days, myalgia, anorexia, malaise, and headache. Fever may persist for 3 to 4 days. Parotitis, lasts at least 2 days, but may persist longer than 10 days. However, mumps infection may present only with nonspecific or primarily respiratory symptoms, or may be asymptomatic.
Mumps infection is most often confused with swelling of the lymph nodes of the neck. Lymph node swelling can be differentiated by the well-defined borders of the lymph nodes, their location behind the angle of the jawbone, and lack of the ear protrusion or obscuring of the angle of the jaw, which are characteristics of mumps. People with mumps are usually considered most infectious for several days before and after onset of parotitis.
Parotitis and Flu
While not a common symptom of flu, swelling of their salivary glands (parotitis) has been reported in persons with laboratory-confirmed influenza infections. To learn more, see 2016-2017 Influenza Update for Health Care Providers: Parotitis and Influenza.
Before there was a vaccine against mumps, the disease was common in the United States and caused complications, such as permanent deafness in children, and occasionally, encephalitis, which could result in death, although very rarely. Before the U.S. mumps vaccination program started in 1967, about 186,000 cases were reported each year, and many more unreported cases occurred. Since the pre-vaccine era, there has been a more than 99% decrease in mumps cases in the United States. From year to year, the number of mumps cases can range from roughly a couple hundred to a couple thousand. However, outbreaks still occasionally occur. In 2006, there was an outbreak affecting more than 6,584 people in the United States, with many cases occurring on college campuses. In 2009, an outbreak started in close-knit religious communities and schools in the Northeast, resulting in more than 3,000 cases. These outbreaks have shown that when people who are sick with mumps have close contact with a lot of other people (such as among students living in dormitories and students and families in close-knit communities) mumps can spread even among vaccinated people. However, outbreaks are much larger in areas where vaccine coverage rates are lower.
The mumps virus replicates in the upper respiratory tract and spreads through direct contact with respiratory secretions or saliva or through fomites. The risk of spreading the virus increases the longer and the closer the contact a person has with someone who has mumps. When a person is ill with mumps, he or she should avoid contact with others from the time of diagnosis until at least 5 days after the onset of parotitis by staying home from work or school and staying in a separate room if possible.
Some complications of mumps are known to occur more frequently among adults than children. Death from mumps is exceedingly rare.
In recent U.S. mumps outbreaks (2006, 2009 to 2010), orchitis occurred in 3.3 to 10% of adolescent and adult males. In 60% to 83% of males with orchitis caused by mumps, only one testis is affected. Such orchitis, even bilaterally, very rarely causes sterility. Among adolescent and adult females in recent outbreaks, mastitis rates have been ≤1% and oophoritis rates have been ≤1%. Other rare complications of mumps include pancreatitis, deafness, meningitis, and encephalitis, which have occurred in less than 1% of cases in recent U.S. outbreaks. There have been no mumps related deaths reported in the United States during recent mumps outbreaks.
Like other infections, there is a theoretical risk that mumps during the early months of pregnancy may cause complications. One study from 1966 that was conducted before the introduction of MMR vaccine reported an association between mumps infection during the first trimester of pregnancy and an increase in the rate of spontaneous abortion or intrauterine fetal death1, but was not found in a more recent study2. Another study with methodological flaws showed that congenital malformations may occur from mumps during pregnancy, but because the author did not compare rates with infants born to women not affected with mumps, these findings must be interpreted with caution3; other papers have not reported similar findings4.
Vaccination is the best way to prevent mumps. This vaccine is included in the combination measles-mumps-rubella (MMR) and measles-mumps-rubella-varicella (MMRV) vaccines. Two doses of mumps vaccine are 88% (range 66% to 95%) effective at preventing the disease; one dose is 78% range (49% to 91%) effective. The first vaccine against mumps was licensed in the United States in 1967, and by 2005, high two-dose childhood vaccination coverage reduced disease rates by 99%. The MMR vaccine protects against currently circulating mumps strains.
See Mumps Vaccination for vaccination recommendations for different groups.
For information about how to classify mumps cases, visit the National Notifiable Diseases Surveillance System (NNDSS) page for mumps or the Laboratory Testing Section of the Manual for the Surveillance of Vaccine-Preventable Diseases (5th Edition, 2012), Chapter 9: Mumps.
Each state and territory has regulations or laws governing the reporting of diseases and conditions of public health importance. These regulations and laws list the diseases that are to be reported and describe those people or groups responsible for reporting, such as healthcare providers, hospitals, schools, laboratories, daycare and childcare facilities, and other institutions.
Contact your state health department for reporting requirements in your state.
For information about reporting mumps cases to CDC, see the Reporting Section of the Manual for the Surveillance of Vaccine-Preventable Diseases (5th Edition, 2012), Chapter 9: Mumps
Mumps in Vaccinated People
During mumps outbreaks in highly vaccinated communities, the proportion of cases that occur among people who have been vaccinated may be high (see example below). This should not be interpreted as meaning that the vaccine is not effective. The effectiveness of the vaccine is assessed by comparing the attack rate in people who are vaccinated with the attack rate in those who have not been vaccinated. In outbreaks in highly vaccinated populations, people who have not been vaccinated against mumps usually have a much greater mumps attack rate than those who have been fully vaccinated.
Vaccination and Mumps Outbreak: an Example
Example: Let’s say that an outbreak occurs among 1,000 people and that 950 of these 1,000 people have received two doses of the vaccine and 50 are unvaccinated (i.e., vaccine coverage is 95%). If there is a 30% attack rate among people who haven’t been vaccinated, 15 unvaccinated people would get the disease. Among the 950 vaccinated people, the attack rate would be 3%, so 29 vaccinated people would get the disease. Therefore, of the 44 people who got sick during the outbreak, the majority (29, or 66%) would have been vaccinated. This doesn’t imply that the vaccine didn’t work. In fact, the people who hadn’t been vaccinated were 10 times more likely to get sick as those who had been vaccinated, it’s just that there were a lot fewer unvaccinated people at risk. Furthermore, if none of the 1,000 people had been vaccinated, the outbreak would have resulted in 300 cases rather than only 44. In this scenario, we would say that the vaccine is 90% effective in preventing the disease after two doses, which is the same as saying that the attack rate in the unvaccinated group is 10 times higher than the attack rate among people who have received two doses of vaccine. The formula to calculate vaccine effectiveness is (attack rate in unvaccinated group minus attack rate in vaccinated group) divided by attack rate in unvaccinated group, or (ARU-ARV)/ARU.
Mumps transmission in healthcare settings, while not common, has occurred in past outbreaks, involving hospitals and long-term care facilities housing adolescents and adults. Information about what measures to take to prevent and control mumps in healthcare settings can be found under the Healthcare Setting section of the Manual for the Surveillance of Vaccine-Preventable Diseases (5th Edition, 2012), Chapter 9: Mumps
In school settings, children in kindergarten through 12th grade should have documentation of two doses of MMR vaccine, except students with medical or religious exemptions. For all incidences, consider the entire group that could have been exposed, including the teachers and staff. Teachers and staff should have their immune status verified (vaccination, serologic evidence of immunity, laboratory confirmation of disease, or birth before 1957). All staff should be educated on how to prevent the spread of mumps and signs and symptoms of the disease.
Exclusion of susceptible students from schools/colleges affected by a mumps outbreaks (and other, unaffected schools judged by local public health authorities to be at risk for transmitting the disease) should be considered as one way to control mumps outbreaks. Once vaccinated, students can be readmitted to school. Students who have been exempted from mumps vaccination for medical, religious, or other reasons should stay home from the 12th day after they were exposed to mumps through the 25th day after the onset of parotitis in the last person with mumps in the affected school.
- Siegel M, Fuerst HT, Peress NS. Comparative fetal mortality in maternal virus diseases. A prospective study on rubella, measles, mumps, chicken pox and hepatitis. N Engl J Med 1966;274(14):768-71.
- Enders M, Rist B, Enders G. [Frequency of spontaneous abortion and premature birth after acute mumps infection in pregnancy]. Gynakol Geburtshilfliche Rundsch 2005;45(1):39-43.
- Bowers D. Mumps during pregnancy. West J Surg Obstet Gynecol 1953;61(2):72-3.
- Siegel M. Congenital malformations following chickenpox, measles, mumps, and hepatitis. Results of a cohort study. JAMA 1973;226(13):1521-4.
- Page last reviewed: July 27, 2016
- Page last updated: October 24, 2016
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