Who should be tested for suspected mumps infection?
Mumps virus can cause illness with an 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.

Clinical diagnosis of mumps may be unreliable, suspected cases of mumps should be laboratory confirmed. As with any disease, lab work should be used in conjunction with clinical presentation (signs and symptoms). The recommendation to laboratory confirm all cases will be re-evaluated as the outbreak progresses.

Mumps should not be ruled out in someone with negative laboratory tests who is vaccinated if they have symptoms consistent with mumps.

A detailed investigation should be conducted for each case with emphasis on accurate and complete immunization history. Recent outbreaks have included many cases who had already received at least one dose of mumps-containing vaccine.

What is the clinical case definition for mumps?
An illness with acute onset of unilateral or bilateral tender, self-limited swelling of the parotid or other salivary gland lasting 2 or more days, and without other apparent cause.

What is a confirmed case of mumps?
Confirmed mumps cases are:

1. laboratory confirmed or
2. meet the clinical case definition and are epidemiologically linked to a confirmed or probable case

What is a laboratory confirmed case of mumps?
Acute mumps infection can be confirmed by the presence of serum mumps immunoglobulin M (IgM), a four-fold rise in serum mumps immunoglobulin G (IgG) titer between acute and convalescent phase serum specimens, positive mumps virus culture, or detection of viral RNA by reverse transcription-polymerase chain reaction (RT- PCR).

Laboratory criteria for diagnosis

• positive serologic test for serum mumps IgM antibody, OR
• four-fold rise between acute- and convalescent-phase titers in serum mumps IgG antibody level by any standard serologic assay, OR
• isolation of mumps virus from clinical specimen, OR
• detection of viral RNA by reverse transcription polymerase chain reaction (RT- PCR)*

* The interpretation of a positive RT- PCR result without demonstration of mumps growth in tissue culture must be interpreted carefully, particularly among persons whose symptoms do not meet the clinical definition of mumps.

What laboratory tests are conducted for mumps and what do they mean?

Serology

• IgM: Mumps is confirmed using mumps IgM antibody testing of serum samples collected as soon as possible after symptom onset for IgM testing. A positive IgM test result indicates current/very recent infection or reinfection. As with any lab test, there can be false positive test results. If the suspected case has received one or more doses of MMR, the IgM response may be missing, delayed, or transient. If the acute IgM is negative, a second serum specimen should be collected. This second specimen should be tested for IgM as a delayed IgM response has been reported to have occurred in mumps cases during the recent UK outbreak, and CDC has observed a similar phenomenon during the 2006 outbreak. UPDATED Jan 5
• IgG: IgG alone is not diagnostic unless you obtain both an acute (can be done as soon after onset as the patient is seen, but ideally four to five days after onset of symptoms) and convalescent (from two to three weeks after onset) blood specimen for serologic tests to determine if a four-fold rise in IgG antibody titer has occurred (e.g., from 1:40 to 1:320). A four-fold increase in IgG titer as measured in plaque-reduction neutralization assays or similar quantitative assays, or a seroconversion from negative to positive in EIA assays from acute to convalescent is considered a positive diagnostic result for mumps. UPDATED Jan 5
  
  In vaccinated persons, the existing IgG will begin to rise soon after exposure and infection. At the time of onset of symptoms and collection of the acute serum, the IgG may already be quite elevated, which would obviate the 4-fold rise in titer expected when comparing acute and convalescent samples.

Also see: Q&As on Lab Testing for Mumps Infection

Virus detection (Direct RT-PCR or virus isolation with sequence analysis)

• Mumps viral RNA may be detected from viral samples prior to onset of parotitis until 5-9 days after parotitis (1-4 days is optimal for virus collection). Among previously immunized suspected cases, mumps virus detection is an important method of confirming the case.
• Sequence analysis of a RT-PCR product derived from a virus isolate or from clinical material confirms the presumptive positive PCR results and provides epidemiologically important information.

What specimens should be collected?
We highly recommend both the collection of serum samples and a mumps viral specimen (buccal swab) on each person with suspected mumps as close to symptom onset as possible.

For the mumps viral specimen a parotid gland/buccal swab is the preferred specimen.

How should specimens be collected and managed?

1. Serologic testing: Collect 7-10 ml of blood in a red top or serum separator tube (SST). Store and ship specimens cold (using ice packs).

   Acute serum: collect within 5 days after symptom onset (at time of diagnosis) UPDATED Jan 5

   Convalescent serum: collect within 2-3 weeks after symptom onset UPDATED Jan 5

2. Mumps viral samples: Collect buccal swab or throat swab as soon as mumps is suspected. Samples may be positive in unvaccinated persons out to 9 days post onset, however among suspected cases that have received 1 or more doses of MMR, virus may be cleared much earlier. A commercial product designed for collection of throat cultures or a plain Dacron swab can be used for the collection of the buccal swab or throat swab (see information below regarding addition of fluids to keep swab moist).
   
   * Synthetic swabs are preferred over cotton swabs which may contain substances that are inhibitory to enzymes used in RT-PCR. UPDATED Jan 5
   

   Parotid Gland/Buccal swab (.pdf): may provide the best viral sample. Massage the parotid gland area (the space between the cheek and teeth just below the ear) for about 30 seconds prior to collection of the buccal secretions. The parotid duct (Stensen’s duct) drains in this space near the upper rear molars. A throat swab (oropharyngeal or nasopharyngeal swab) can also be collected and added together with the buccal swab.

   Place swab in a tube containing 2-3 mls of viral transport medium or cell culture medium (MEM or Hanks Balanced Salt Solution) or other sterile isotonic solution (phosphate buffered saline). The presence of protein, for example 1 percent bovine albumin, 0.5 percent gelatin, or 2 percent serum, stabilizes the virus which otherwise loses 90-99 percent infectivity within 2 hours at 4C in a protein-free medium. UPDATED Jan 5

   Keep samples cold (4C). If there is more than 1 day delay in shipping the samples to the state lab or CDC for testing, the buccal swab or throat swab is best preserved at -70C. Ship the viral specimens using ice packs or dry ice*. Avoid freeze-thaw cycles.

*If shipment contains both serum and viral samples, ship together by overnight service on cold packs (do not freeze serum).

Where do I send the laboratory specimens for testing?

First, contact your health department to determine where to submit specimens and how to ship them.

To send specimens to CDC use form 50.34 (see clarification note below).

Clarification note: For the onset date [top of CDC-50.34 (FRONT)], please provide the onset date of parotitis or jaw swelling. Under State Health Dept Laboratory Address [top of CDC-50.34 (FRONT)], please also provide a contact name with telephone number or email address. Most important information to include: Type of viral specimen and date collected, serum date, MMR vaccination history [date(s) if known], clinical signs and symptoms, patient date of birth or age, and onset date of parotitis or jaw swelling.

State Health departments and Public Health Labs may forward specimens for confirmatory testing.

Ship to:
Centers for Disease Control and Prevention
DASH / Unit 81
Attn: Dr. William J. Bellini
1600 Clifton Road
Atlanta, GA 30333

Call Jennifer Rota at 404-639-1156 or e-mail at jrota@cdc.gov for additional information and to provide the details of the shipment.

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