Measles Virus by Qualitative PCR

Last Literature Review: April 2025 Last Update:

Measles is a highly communicable respiratory disease characterized by symptoms such as fever, malaise, cough, conjunctivitis, coryza, Koplik spots, and a maculopapular rash that radiates downward from the head. ,  Molecular testing can be used to diagnose measles infection and differentiate a rash induced by a recent vaccination from a wild-type measles virus infection.  Samples for RNA detection should be collected as soon as possible after rash onset, as viral shedding declines with time after rash. 

Test Interpretation

Analytic Sensitivity/Specificity

Real-time PCR tests for measles allow for earlier detection of the virus as compared to measles IgM antibodies. PCR tests demonstrate a sensitivity of 94% and a specificity 99%. 

Results

Measles Virus Vaccine StrainMeasles VirusInterpretation
DetectedNot detectedDetection of measles virus vaccine strain RNA indicates that this patient’s symptoms were likely due to vaccine reaction following recent vaccination; individuals with vaccine reactions are not contagious
Not detectedDetected

Detection of wild-type measles virus RNA is consistent with a diagnosis of measles infection

Infected patients are at high risk of transmitting the virus to unimmunized individuals

Hospital infection control and a state or local public health laboratory should be notified immediately

Not detectedNot detected

Negative for measles virus RNA

Consider other viral and noninfectious causes for patients who present with rash

Limitations

  • Specimens with low levels of vaccine strain measles virus may be reported as wild type due to the lower sensitivity of the vaccine-specific target (MeVA) compared with the pan-measles virus target (MeV).
  • A negative result does not rule out the presence of PCR inhibitors in the patient specimen or assay-specific nucleic acid in concentrations below the level of detection of this assay.
  • Serology testing may be indicated if measles is still suspected following a negative result.
  • This assay does not enable the definitive identification of wild-type/vaccine strain coinfections.

References

  1. Red Book - Measles

    Kimberlin D. Measles. In: Bannerjee R, Barnett E, Lynfield R, et al, eds. Red Book: 2024–2027 Report of the Committee on Infectious Diseases. American Academy of Pediatrics; 2024:570-585.