Guideline for Measles Virus Testing

Measles virus (rubeola) is a highly contagious, vaccine-preventable virus that causes a respiratory infection characterized by fever, rash (classically appearing a few days after fever onset and starting on the face then spreading downward), and at least one of: cough, coryza (runny nose), or conjunctivitis.

Despite being vaccine-preventable, cases have recently increased regionally and nationally, leading to the University of Washington offering Measles Virus Qualitative PCR [MEVQLT] testing starting May 4, 2026. This test supports ongoing public health testing efforts to identify acute measles virus infections.

Acute Measles Testing

Determining if Testing is Indicated

Testing for acute measles virus infection should be targeted to patients with compatible clinical features and epidemiologic risk factors. Early recognition, immediate airborne isolation, and prompt communication with Infection Prevention and public health are critical when measles infection is suspected. To facilitate communication, the ordering provider MUST notify the local health jurisdiction (LHJ) for the patient's county of residence (King County: 206-296-4774, Interactive Map of LHJs) of any suspected measles cases at the time infection is suspected (prior to testing).

Measles Virus Qualitative PCR [MEVQLT] should only be ordered in cases with a high clinical suspicion for acute measles infection. See the Washington State Department of Health Evaluation Worksheet for guidance evaluating patients for possible measles infection. Briefly, measles is highly suspected if patients have:

• Fever ≥101.3°F (38.3°C) AND
• Generalized maculopapular rash AND
• At least one of: cough, coryza (runny nose), or conjunctivitis
• Especially when there is:
  • International travel within 21 days
  • Domestic travel to an area with known measles transmission (Johns Hopkins US Measles Tracker)
  • Known or suspected measles exposure (WA State Measles Exposure Locations Map)
  • Unvaccinated or undocumented MMR vaccine status

Testing patients before rash onset is discouraged because a negative PCR result early in illness does not exclude evolving measles infection and repeat testing may be required if rash develops later.

Patients suspected of having an acute measles infection should immediately be placed under airborne respiratory precautions and all samples must be collected in the patient's room. Patients should NOT go to outpatient blood draw or other congregate settings if acute measles infection is suspected.

Measles PCR testing should not be used for broad screening of patients with nonspecific rash or respiratory illness. Testing is not recommended for isolated fever, isolated respiratory symptoms, or nonspecific rash without compatible clinical features and epidemiologic risk factors.

Ordering Acute Measles Testing

At UW Medicine, the primary diagnostic test for acute infection is Measles Virus Qualitative PCR [MEVQLT]. This test includes both pan-measles and vaccine strain measles targets to differentiate acute measles infection from recent vaccination.

A complete evaluation for acute measles infection includes 3 samples:

1. Measles Virus Qualitative PCR [MEVQLT] testing of a respiratory (nasopharyngeal or oropharyngeal) swab
2. Measles Virus Qualitative PCR [MEVQLT] testing of a urine sample
3. Collection of a serum sample for possible measles IgM testing pending PCR results
   • This sample should be ordered as Measles IgM Draw and Hold Sample [MEVDRH] and will be stored for 2 weeks
   • If PCR testing is negative, the sample was collected ≥4 days post-rash onset, and clinical suspicion for measles infection remains high, this sample is available to be forwarded to the Washington State Public Health Laboratory for measles IgM testing.
   • Measles IgM testing must be coordinated with your facility's Infection Prevention and requires LHJ approval.
   • After receiving LHJ approval for IgM testing, an add on (LADDON) order for Measles IgM Add On (Sendout) [MEVIGM] including details of approval should be placed to direct the UW lab to send the sample to the state lab for IgM testing.

As of June 1, 2026, an Acute Measles Order Panel is available in Epic to simplify ordering.

Specific ordering workflows differ slightly by location:

• At UW Medical Center Montlake, UW Medical Center Northwest, Harborview Medical Center, and UW Medicine Primary Care clinics, testing should be ordered by the primary clinical team when criteria for suspected measles (above) are met. Infection Prevention teams will be automatically notified of all PCR orders, but clinical teams should also contact their facility's Infection Prevention during daytime hours.
• At Fred Hutch, ordering remains restricted to Infection Prevention. Providers should place the Acute Measles Rule-Out, FHCC Outpatient Only order to facilitate review and testing.
  
  

Outside clients should order Measles Virus Qualitative PCR [MEVQLT] testing from UW and coordinate any possible measles IgM testing with their respective public health laboratory directly.

Other Measles Testing

Measles IgG Serology (Immune Status)
Rubeola (Measles) Immune Status [RBIS] is used to evaluate evidence of immunity and is not appropriate for diagnosing acute measles infection.

IgG testing may be used in situations such as:

• Assessing immune status in individuals with uncertain or undocumented MMR vaccination history.
• Occupational or pre‑employment immunity screening.
• Evaluation of immune status in immunocompromised patients when vaccination history is unclear.

Detection of measles IgG generally indicates prior vaccination or past infection and correlates with immunity. IgG testing should not be used to evaluate suspected acute measles because antibodies may already be present in vaccinated individuals and do not distinguish remote immunity from current infection.