What
specimens should be collected
from patients meeting the clinical
case definition?
CDC
recommends that a blood specimen and buccal/oral
swab be collected from all patients
with clinical features compatible with mumps. UPDATED
Jan 5
When
is the best time to collect clinical
specimens?
In unvaccinated persons,
the best time to collect serum is between
3 to 5 days from the time symptoms are
evident. Buccal/oral swabs should also
be collected during this time period.
If a patient presents
earlier than this, it is still useful to collect serum and
viral specimens. UPDATED
Jan 5
The
experience we have so far (supported
by published studies; see references
below) suggests that serum IgM may
be negative in up to 50-60% of acute
serum samples among patients who have
been previously immunized, so a case
in a vaccinated person should not
be ruled out on the basis of a negative
IgM. If the acute IgM is negative, a second
serum specimen should be collected. UPDATED
Jan 5
Why
should I ask for viral samples
such as buccal swabs
in addition to the serum sample?
Buccal
swabs samples can be tested
for the presence of mumps virus (growth
in culture) or mumps viral RNA using standard
reverse transcriptase - polymerase chain-reaction
(RT-PCR) methods. UPDATED
Jan 5
What
is the gold standard for laboratory
confirmation of mumps?
Virus
culture. Laboratories are strongly encouraged
to perform cell culture isolation of mumps
from buccal/oral swabs specimens.
Primary monkey kidney cells and Vero cells
have been used successfully. Detection of mumps in culture
can be done using immunofluorescent antibody staining or
standard RT-PCR. UPDATED
Jan 5
What
serological tests are used at
CDC to diagnose mumps?
To
detect mumps IgM, a capture EIA (non-quantitative)
that uses recombinant mumps nucleocapsid
(N) protein as antigen is used. A commercial,
indirect EIA (non-quantitative) is used
for detection of IgG.
What
serological tests are available
for use in the Public Health Laboratories?
There
are commercially available immunofluorescence
antibody assays for detection of mumps
IgM and some EIA kits may be obtained.
Since these assays are not FDA-approved
for laboratory diagnosis of mumps cases,
each laboratory must validate these tests
independently.
If
the suspected case has a positive
IgG and negative IgM result, can
mumps infection be ruled out?
In
an outbreak setting, no. Previously vaccinated
persons who are exposed to mumps will
generally have existing, detectable serum
IgG.
What
is the protective neutralization
titer for mumps?
There
is no known protective neutralization
titer or any other immune parameter(s)
that correlates with protection from mumps
disease. Immunized persons who are exposed
will normally experience a boost in IgG
titer.
Will
persons infected with mumps who
are symptomatic and have a history
of one or two doses of MMR have
an IgM response?
The
IgM response to mumps infection in vaccinated
persons is highly variable and may be
absent. In unvaccinated cases, IgM is
present by day 5 post onset of symptoms
and peaks at about 1 week; IgM can be
present for at least 6 weeks.
Is
it possible to demonstrate a 4-fold
rise in titer between paired serum
samples (acute and convalescent)
among cases of mumps with a history
of 1 or 2 doses of MMR?
It
may not be possible. 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, and obviate the 4-fold
rise observed in convalescent serum specimen.
What
etiologic agents are likely to
interfere with serological assays
(produce false positive) for mumps?
Parainfluenza
viruses 1 and 3.
What
does a positive result from RT-PCR mumps test from clinical material
mean?
A
positive RT-PCR signal indicates the
presence of mumps viral RNA. The positive
result should be used only to support
a clinical diagnosis of mumps since persons
recently immunized against mumps may have
limited viral shedding following vaccination.
Why
attempt to isolate mumps virus
in cell culture?
Virus
isolation is considered the best method
to detect infection. Virus can be detected
when IgM antibodies or IgG titer rise
are not detected. Additionally, it provides
virus that can be used for sequence studies. Finally, isolation
studies are less likely than PCR assays to give false positive
results because of contamination.
Why
should PCR products from representative
mumps cases and mumps viral isolates
be submitted to CDC for sequence
analysis?
The
sequence of the PCR product will confirm
positive PCR reactions. In addition, the
sequence of the mumps short hydrophobic
(SH) gene is used to assign mumps viruses
to one of 12 recognized genotypes. The
sequence information will help to identify
the source of the virus, and can provide
confirmation of suspected epidemiologic links.
Where
can I find RT-PCR and real time
RT-PCR protocols for mumps?
Protocols
for both a standard RT-PCR and a real
time RT-PCR targeting the short hydrophobic
(SH) gene of mumps virus have been posted
on the CDC web page (http://www.cdc.gov/nip/diseases/mumps/#lab).
UPDATED Jan 5
Where
do I obtain material for PCR and
virus isolation controls?
CDC
can provide a sample of RNA that has been
purified from cells infected with mumps
virus. This material is ready to use in
RT-PCR assays with any set of primers.
If laboratories would like to produce
their own RNA samples or require a positive
control for virus isolation, CDC can provide
a sample of wild-type mumps virus. Public
health laboratories or laboratories affiliated
with state public health laboratories
may send request for mumps RNA or virus
to jrota@cdc.gov.
A
sample tests negative for mumps
RNA by RT-PCR or negative for
mumps virus by isolation. Do these
results rule out mumps infection?
No.
These samples could be negative because
the amount of virus shed at the time of
sample collection was very low. Inadequate
specimen collection, processing, shipping
or storage can also significantly reduce
the likelihood of detecting mumps virus
or mumps RNA. UPDATED Jan 5
Among
symptomatic persons who have received
1 or more doses of MMR, the virus
may be cleared rapidly. The results
to date do not indicate that RT-PCR
for mumps among vaccinated persons
has provided a diagnostic tool that
is superior to IgM testing. However,
samples collected when the patient
first presents with symptoms have
the best chance of having a positive
result by RT-PCR.
References
Gut
JP. Lablache C. Behr S. Kirn A. Symptomatic
mumps virus reinfections. Journal
of Medical Virology. 45(1):17-23,
1995.
Narita
M. et al. Analysis of mumps vaccine
failure by means of avidity testing
for mumps virus-specific immunoglobulin
G. Clinical & Diagnostic
Laboratory Immunology. 5(6):799-803,
1998.
Sartorius,
B, et al. An outbreak of mumps in
Sweden, February-April 2004. Eurosurveillance.
1:10 (9), 2005.
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