Rubella Virus

The information provided is offered as a resource for Wisconsin Laboratories and Health Care Facilities.

• All suspected cases of rubella should be immediately reported to the local public health department.

• Note that rubella 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 is 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 Wisconsin State Laboratory of Hygiene (WSLH) recommends collection of specimens for serologic and culture and real-time polymerase chain reaction (PCR) testing for all suspect cases of rubella. Specimens for culture and PCR testing should be collected at the same time as the acute serum for rubella IgM serology.
    
    
    • Clinical specimens for viral isolation are often helpful to confirm a positive serum result and for viral surveillance of rubella genotypes.

• Specimen Collection Instructions
  
  
  • Combined Throat and Nasopharyngeal Swabs (This is the preferred specimen for rubella.)
    
    
    • 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 rubella is suspected, preferably within the first 5 days of rash onset, but they may be collected between 2-3 days before rash onset to 14 days after rash onset.
      
      
      • Throat swab:  Swab the posterior pharynx and tonsillar areas, avoiding the tongue (tongue depressor may be helpful). The mucosa behind the uvula and between the tonsils should be gently swabbed with a back-and-forth motion.
      
      
      
      • Nasopharyngeal swab:  Insert sterile swab into nasopharynx, rotate and remove.  For additional instructions or instructional video, click here: http://content.nejm.org/cgi/content/full/NEJMe0903992/DC1
      
      
      
      • 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 (Throat or NP specimens have a higher rate of rubella virus recovery than urine.)
    
    
    • First-voided morning urine usually contains the highest concentration of infected cells.
    
    
    
    • 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.
    
    
    
    • The presence of rubella IgM antibody or a significant change in rubella antibody titer in acute and convalescent serum specimens is usually considered confirmation of acute rubella infection.
    
    
    
    • The acute phase serum should be collected as early as possible (within 7–10 days) after onset of illness, with the second (convalescent) serum collection 14–21 days later.
    
    
    
    • Previous vaccination may have an effect on the development of IgM antibodies or the development of a significant change in antibody titer (as with mumps and rubeola), but has not been clearly documented.

• Specimen Submission Instructions
  
  
  • When submitting specimens to the WSLH for rubella 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 rubella 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.
    
    
    
  • Rubella IgM Serology Testing: The WSLH performs rubella IgM serology testing within 24 hours of receipt.
    
    
    • Aliquots of serum specimens will be forwarded to CDC for additional testing as appropriate.
    
    
    
  • Rubella IgG Serology Testing:  The WSLH can perform rubella IgG serology testing on a single serum to assess an individual’s immune status for rubella.  IgG serology testing of a single serum is NOT used for diagnosis of an acute case.
    
    
    • Rubella serology of paired sera can be of value, but previous vaccination may have an effect on the development of IgM antibodies or the development of a significant change in antibody titer (as with mumps and rubeola), but has not been clearly documented.
    
    
    
    • 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.
    
    
    
    • The WSLH will forward aliquots of paired sera to CDC for rubella IgG antibody testing as appropriate.
    
    
    
  • Rubella Culture Testing:  Isolation of rubella virus is not recommended as a routine method to diagnose rubella, 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 rubella culture.

• WSLH Test Results
  
  
  • Negative results do not rule out rubella 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 rubella virus or rubella 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.
    
    
    
  • IgM Serology Results
    
    Rubella IgM:    Negative
    This result indicates that no IgM antibody to rubella virus was detected.  The absence of rubella-specific IgM antibody may indicate that this patient is not currently infected with rubella.  If this serum was collected prior to onset of rash, IgM may not yet be at detectable levels.  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 rubella virus.
    
    Rubella IgM:  Positive
    This result indicates that IgM antibody to rubella virus was detected.  The presence of rubella-specific IgM antibody usually indicates that this patient was recently infected or immunized with rubella virus.
    
    Rubella IgM:  Equivocal
    This result indicates that the testing performed cannot definitively determine whether a significant level of IgM antibody to rubella virus was or was not detected.  This does not rule out, nor confirm, a recent or current infection with this agent.  Please submit a second (convalescent) serum, collected in 2-3 weeks, to confirm diagnosis.
  
  
  
  • PCR Test Results
    
    Rubella Virus PCR:  Rubella virus RNA detected.
    This result indicates that testing has detected rubella virus genetic material in the specimen; this specimen is considered positive for rubella.
    
    Rubella Virus PCR:  No Rubella virus RNA detected.
    This result indicates that testing was not able to detect rubella virus genetic material in the specimen.  A negative result, however, does not rule out infection with rubella virus, as many factors in the collection and transport of the specimen could significantly reduce the likelihood of detecting rubella virus RNA.
    
    Rubella Virus PCR:  Equivocal
    This initial result indicated a low level of mumps virus RNA, but repeat testing failed to confirm the initial result.
    
    Rubella 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.

Resources

• CDC Rubella Webpage

• CDC Measles, Mumps, Rubella, Varicella Vaccine Safety Webpage

• MedlinePlus Health Topic Rubella Webpage

• Wisconsin Department of Health Services Rubella Disease Fact Sheet

• Wisconsin Department of Health Services Childhood Vaccine Information and Schedules Webpage

• Wisconsin Department of Health Services Immunization Program Rubella Webpage

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