Mumps

The mumps outbreak in Iowa and other midwestern states appears to be slowing.¹ However, it is not yet contained. As college students-the age group hardest hit-return home and engage in summer travel, there is a very real possibility, because of the illness's long incubation period (12 to 25 days), that mumps will spread. Are you prepared?

WHY CONTAINMENT MATTERS

The classic symptom of mumps is swelling of the parotid salivary gland (or, less commonly, of the submandibular and sublingual glands), accompanied by such nonspecific symptoms as myalgia, anorexia, headache, and low-grade fever. Salivary gland swelling results in the swollen cheeks and neck commonly associated with the illness (Figure).

The most severe complications of mumps-hearing loss and encephalitis-are quite rare. Permanent sequelae and death are also rare. However, aseptic meningitis develops in 10% of patients, and complications that involve other organs occur more frequently in adults than in children. Between 30% and 40% of post-pubertal male patients experience orchitis, and 30% or more of female patients older than 15 years experience mastitis.² Rarely, orchitis can result in sterility. Pancreatitis or oophoritis may develop in some patients. Also, mumps infection in the first trimester of pregnancy can result in spontaneous abortion.

Thus, stemming the spread of illness-especially among the young adult population that so far has been most susceptible-is highly important.

CHARACTERISTICS OF THE CURRENT OUTBREAK

The mumps outbreak that began in the Midwest in late March has affected at least 3000 persons-more than 1600 in Iowa and over 1300 in 7 other states (South Dakota, Nebraska, Kansas, Missouri, Illinois, Wisconsin, and Pennsylvania).¹ The Iowa Department of Public Health reports that about 40% of cases have involved 18- to 25-year-olds.¹

The concentration of illness in young adults is thought to result from more persons in this population having received only 1 dose of measles-mumps-rubella (MMR) vaccine instead of the currently recommended 2 doses-coupled with the close living conditions of college life.³ Although the MMR vaccine has been in use since 1967, administration of a second dose did not become routine practice until 1989. Better 2-dose coverage rates among those born since then are believed to be responsible for the lack of outbreaks in younger children and in schools. Persons born before 1957 are presumed to have been exposed to the disease during childhood and thus to be naturally immune.

MAKING THE DIAGNOSIS

The role of early diagnosis in stemming the spread of mumps cannot be underestimated (Box). The clinical case definition of the illness is "acute onset of unilateral or bilateral tender, self-limited swelling of the parotid or other salivary gland, lasting 2 or more days, without other apparent cause."²

The swollen cheeks seen in classic cases may be hard to miss. However, only 30% to 40% of infections produce acute parotitis, and 15% to 20% of infected persons are asymptomatic. In many patients- especially children younger than 5 years-symptoms are nonspecific and can easily be mistaken for those of other viral respiratory illnesses.² Even in patients who present with parotitis, other causes of salivary gland enlargement need to be considered (Table).

Thus, epidemiologic factors can play an important role in the identification of mumps. It is important to ask patients about recent travel and other contacts; recent illness in family, friends, and associates; and vaccination history.

In situations where health care providers are not familiar with mumps, laboratory confirmation increases in importance. There are several ways in which mumps can be confirmed by laboratory testing. These include:

• A positive result on a serologic test for mumps IgM antibody.

• A 4-fold rise between acute-phase and convalescent-phase titers of mumps IgG antibody level.

• Isolation of mumps virus from a clinical specimen.

• Detection of mumps virus RNA by reverse transcription polymerase chain reaction.²

Virus culture is the gold standard for laboratory confirmation of mumps. Serologic tests for mumps IgM antibody may be negative in more than 50% of infected patients who were previously immunized, and IgG antibody levels in vaccinated persons are likely already to have risen to near-peak levels by the time acute sera are collected.⁴ Thus, the diagnosis cannot be ruled out on the basis of serologic testing in those previously vaccinated.

Cases that meet the clinical case definition but have not been epidemiologically linked to mumps infection and have not been confirmed by laboratory testing (or have yielded inconclusive results on such tests) are considered probable cases. Cases that have been laboratory-confirmed or that meet the clinical case definition and have been epidemiologically linked to a confirmed or probable case of mumps are considered confirmed cases. Both probable and confirmed cases of mumps should be reported in accordance with state and local health department guidelines.

Quarantine is not required but isolation is recommended.² Ask any patient in whom mumps is diagnosed to stay home from work or school for 9 days after onset of symptoms.

EFFECTIVE PREVENTION

Mumps is spread through contact with respiratory secretions, saliva, or fomites. In addition to the 9 days after symptom onset, the 3 days before the beginning of parotid swelling can also be an infectious time.³ Moreover, infected persons with nonspecific symptoms and those who are asymptomatic can transmit the disease as well. These features of the illness, coupled with its long incubation period, create abundant opportunities for unwitting exposure. Thus, although prompt identification of new cases plays an important role in preventing further spread of the infection, the CDC continues to stress that achieving high levels of immunization against mumps is the best preventive strategy.³

The MMR vaccine has an effectiveness of 70% to 80% in persons who receive a single dose. Even in persons who receive the recommended 2 doses, effectiveness is only 80% to 90%.² Because the vaccine does not "take" in 10% or more of those who receive it, very high levels of coverage are necessary to establish herd immunity, which impedes the establishment and spread of a newly introduced infection. During outbreaks (such as the present one), it is especially important to ensure that as many persons as possible have received 2 doses of the MMR vaccine.

Health care workers. Because they may be at increased risk for acquiring mumps during an outbreak and transmitting it to patients, health care workers who do not still have immunity from childhood are advised to receive 2 doses of MMR vaccine. Although persons born before 1957 are generally presumed to be immune, those who do not have a history of physician- diagnosed mumps may still be susceptible and should consider vaccination in the event of an outbreak.² Health care workers can continue to work after being vaccinated; there are no reports of transmission of mumps from vaccinees to susceptible contacts.²

Seroconversion is seen in more than 80% of vaccinated persons 4 weeks after vaccination, and in more than 90% 5 weeks after vaccination. However, seroconversion may not always result in immunity.²

Young children. No changes in the standard vaccination schedule for children are recommended as a result of the current outbreak. Administer the first dose of MMR vaccine as close to a child's first birthday as possible and the second dose between ages 4 and 6 years. If the outbreak begins to affect preschool-age children, the second dose may be administered early, but no earlier than 28 days after the first one.²

Young adults. Vaccination of persons in this age group is of utmost importance. The CDC urges all institutions for post-high school education to require that students receive 2 doses of MMR vaccine or provide other acceptable evidence of immunity before enrollment. In Iowa, recent efforts to make sure that as many 18- and 19-year-olds as possible receive both doses of the vaccine have helped stop the spread of mumps on that state's college campuses.¹ (Unfortunately, attempts to reach Iowa's 20- to 25-year-olds have been less successful; a free statewide vaccination program aimed at young adults had a low turnout.¹)

Pregnant and breast-feeding women. Pregnancy is a contraindication to vaccination. Women who are pregnant should not receive MMR vaccine, and women who are vaccinated should avoid pregnancy during the 4 weeks afterwards.² However, breast-feeding is not a contraindication, and both women and infants who are breast-feeding may be safely vaccinated.²

Exposed persons. Mumps vaccine does not prevent mumps in persons who have already been infected with the virus.²

References:

REFERENCES:

1.

Jones T. Mumps spread slows in Iowa, but officials worry about college students bringing virus home.

Chicago Tribune

. May 10, 2006. Available at:

http://www.chicagotribune.com/news/nationworld/chi-0605100149may10,1,4673700. story?coll=chi-newsnationworld-hed

. Accessed May 10, 2006.

2.

Centers for Disease Control and Prevention.

Mumps--Technical Q&As

. Available at:

http://www.cdc.gov/nip/diseases/mumps/mumps-tech-faqs.htm

. Accessed May 10, 2006.

3.

Centers for Disease Control and Prevention.

Press Briefing on Mumps Outbreak In the Midwest with Dr Julie Gerberding, and Dr Jane Seward

. April 19, 2006. Available at:

http://www.cdc.gov/od/oc/media/transcripts/t060419.htm

. Accessed May 19, 2006.

4.

Centers for Disease Control and Prevention.

Laboratory Testing for Mumps Infection

. Available at:

http://www.cdc.gov/nip/diseases/mumps/lab-test-faqs.htm

. Accessed May 19, 2006.

5.

Mumps outbreak at a summer camp--New York, 2005.

MMWR

. 2005;55: 175-177.