Measles Virus (Rubeola)
The information provided is offered as a resource for Wisconsin Laboratories and Health Care Facilities.
- All suspected cases of measles should be immediately reported to the local public health department.
- Note that measles testing at the Wisconsin State Laboratory of Hygiene (WSLH) and the cost of specimen transport will be performed on a "fee for service" basis, unless fee-exempt testing and transport are approved by the local health department or the Wisconsin Division of Public Health.
- Specimens for Testing
- Specimens to be collected in most cases are:
- Acute serum
- Throat and nasopharyngeal swabs (combined in one vial)
- Urine specimen
- Specimen collection and transport instructions can be found below.
- In accordance with CDC guidelines, the WSLH recommends collection of specimens for serologic and culture and real-time polymerase chain reaction (PCR) testing for all suspect cases of measles. Specimens for culture and PCR testing should be collected at the same time as the acute serum for measles IgM serology.
- Clinical specimens for viral isolation are extremely important for molecular epidemiologic surveillance to help determine the geographic origin of the virus and the viral strains circulating in the United States.
- A repeat serum for measles IgM antibody should be collected if the first serum was collected within three days of rash onset and is negative for IgM antibody to measles.
- Specimen Collection Instructions
- Combined Throat and Nasopharyngeal Swabs
- WSLH recommends collection of a throat swab AND a nasopharyngeal swab, combined in the same vial of virus transport medium.
- Collect specimens as soon as measles is suspected, preferably within the first 3 days of illness, but no later than 10 days after rash onset.
- Synthetic swabs (e.g., Dacron) are required for specimen collection. Do not use cotton or calcium alginate swabs as they may be inhibitory to enzymes used in PCR.
- Place both swabs in a single tube of virus transport medium; any commercially available virus transport medium is acceptable.
- Maintain specimen at refrigerator temperature prior to transport. Transport at refrigerator temperatures using kool-packs.
- Urine Samples
- First-voided morning urine usually contains the highest concentration of infected cells. Virus can be present in the urine even a few days before rash appears and begins to diminish a few days following rash onset.
- Collect 10-50 ml of urine in an empty container; do not add virus transport medium.
- Maintain the urine specimen at refrigerator temperature prior to transport. Transport at refrigerator temperatures using kool-packs.
- Serum Samples
- Collect 7-10 ml of blood in a red top or serum separator tube (SST). Store specimens at refrigerator temperature. Transport at refrigerator temperatures using kool-packs.
- A repeat serum specimen should be collected and tested if IgM serology testing is negative for specimens collected within 72 hours of rash onset.
- Paired sera can be of value for patients with no history of vaccination or with seronegative acute specimens. Collect acute serum as soon after onset as possible and collect the convalescent serum 2-3 weeks later to determine if a significant change in IgG antibody titer has occurred.
- Specimen Submission Instructions
- When submitting specimens to the WSLH for Measles testing, include a completed requisition form (CDD form A or B). If you do not have a WSLH requisition form available, you may substitute the "General Outbreak" form available at General Outbreak Response Form (Word DOC).
- Be sure to complete the submitter information, along with complete patient information, and the agent and test requested.
- Specimen Transport Instructions
- All specimens should be transported to the WSLH as soon as possible at refrigerator temperatures using kool-packs.
- Transport arrangements and costs are the responsibility of the submitter unless other arrangements are agreed to by the WSLH.
- Testing at the WSLH
- PCR Testing: The WSLH will perform measles PCR testing of aliquots of combined nasopharyngeal/throat swab and urine specimens within 24 hours of specimen receipt.
- The WSLH may perform culture and/or PCR for other agents that can cause similar symptoms; non-requested testing will be performed at no cost to the submitter.
- Aliquots of nasopharyngeal/throat swab and/or urine specimens will be forwarded to CDC for culture and characterization as appropriate.
- Measles IgM Serology Testing: The WSLH will perform measles IgM serology testing of acute serum within 24 hours of specimen receipt.
- Aliquots of serum specimens will be forwarded to CDC for additional testing as appropriate.
- Measles IgG Serology Testing: The WSLH can perform measles IgG serology testing on a single serum to assess an individual's immune status for measles. IgG serology testing of a single serum is NOT used for diagnosis of an acute case.
- Measles IgG serology of paired sera can be of value for patients with no history of vaccination or with seronegative acute specimens. Collect acute serum as soon after onset as possible and collect the convalescent serum 2-3 weeks later to determine if a significant change in IgG antibody titer has occurred.
- Measles IgG serology of paired sera is available at the CDC. The WSLH will forward aliquots of appropriate specimens to CDC for testing.
- Measles IgG serology of paired sera is not recommended for diagnostic testing of previously vaccinated individuals.
- Measles Culture Testing: Isolation of measles virus is not recommended as a routine method to diagnose measles, but virus isolates are extremely important for molecular epidemiologic surveillance to help determine the geographic origin of the virus and the viral strains circulating in the United States.
- The WSLH will forward aliquots of appropriate specimens to the CDC for measles culture.
- Specimens for virus culture should be collected at the same time as samples taken for serologic testing. Specimens for culture should be collected within 10 days (preferably within 3 days) of rash onset.
- WSLH Test Results
- Negative results do not rule out measles infection due to the following:
- The amount of virus shed at the time of sample collection may have been too low to be detected.
- Inadequate specimen collection, processing, shipping or storage can significantly reduce the likelihood of detecting measles virus or measles RNA.
- Previously vaccinated individuals may not have a detectable IgM response.
- The full clinical and epidemiologic picture should be taken into consideration when interpreting test results.
- Measles IgM Serology Results
Measles IgM: Negative
This result indicates that no IgM antibody to measles virus was detected. The absence of measles-specific IgM antibody may indicate that this patient is not currently infected with measles, but IgM antibody may be absent or transient in persons who were previously immunized. A negative result does NOT rule out recent or current infection with measles virus.
Measles IgM: Positive
This result indicates that IgM antibody to measles virus was detected. The presence of measles-specific IgM antibody usually indicates that this patient was recently infected or recently immunized with measles virus.
Measles IgM: Equivocal
This result indicates that the testing performed cannot definitively determine whether a significant level of IgM antibody to measles virus was or was not detected.
- Measles Virus PCR Test Results
Measles Virus PCR: Indeterminate
This result indicates that this specimen was suboptimal or exhibited inhibition in the PCR assay, so an accurate result could not be obtained. If clinically warranted, repeat testing is suggested.
Measles Virus PCR: Equivocal
This result indicates that the initial test results indicated the presence of measles virus RNA, but repeat testing did not confirm the initial result.
Measles Virus PCR: Measles virus RNA detected.
This result indicates that testing has detected measles virus genetic material in the specimen; this specimen is considered positive for measles.
Measles Virus PCR: No Measles virus RNA detected.
This result indicates that testing was not able to detect measles virus genetic material in the specimen. A negative result, however, does not rule out infection with measles virus, as many factors in the collection and transport of the specimen could significantly reduce the likelihood of detecting measles virus RNA.
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