Laboratory Testing for Measles

Measles is a highly communicable viral disease that is a reportable disease under the Health Protection and Promotion Act, 1990, Chapter H.7, Ontario Regulation 558/9.  It is characterized by a prodromal fever, cough, conjunctivitis, coryza and small spots with white or bluish-white centers on the inside of the mouth and throat ("Koplik's spots").   These symptoms may last for 1 to 2 weeks.  Three to seven days after the start of the symptoms, a characteristic maculopapular rash typically appears on the face, then progresses down the body and lasts at least 3 days.

Measles is airborne and spread by close personal contact or direct contact with the respiratory secretions of a case, and less commonly through secretions on contaminated articles.  The incubation period is 7 to 21 days, usually 14 days.  Communicability is from 4 days before to 4 days after the onset of rash.

Laboratory testing is required for any suspect case of measles and must include both acute serology and virus detection by PCR.  Convalescent serology is recommended if acute serology and virus detection are negative or indeterminate.  Results must be reported to Ottawa Public Health.

Acute Serology

A blood specimen for measles antibodies, IgM and IgG, should be collected ideally within 7 days after the onset of the rash.

Virus Detection by PCR

A nasopharyngeal swab or aspirate, or a throat swab, should be obtained within 4 to 7 days after the onset of rash (specimens should be collected using the Viral Transport Media (VTM) collection kit, item # N-0081; if provided by the Public Health Ontario Laboratories, these swab kits contain pink medium)

AND

Approximately 50 ml of clean catch urine should be collected in a screw top sterile container within 14 days after the onset of rash.

Convalescent Serology

A blood specimen should be collected 7 to 10 days after the onset of rash and a minimum days after the acute sample.  The requisition should specify that the blood specimen of 5 is for "convalescent measles serology".

Storage and Transport Requirements

All virus detection specimens must be stored in the refrigerator and be shipped cold to the laboratory.  The measles virus is stable at 4o C for 3 days

Laboratory Requisition Requirements

For suspect cases, the requisition must include the following relevant clinical information:

  • Ordering physician's name and telephone number
  • Measles IgG and IgM marked as STAT
  • Type of specimen (i.e. nasopharyngeal swab)
  • Immunization history, exposure history and travel history outside Ottawa for the 21 days prior to the first symptom
  • Clinical symptoms such as fever, cough, and rash, and date of onset
  • Reason for testing (i.e. "to diagnose disease", "measles testing")

Laboratory options for testing

  • CHEO (Children's Hospital of Eastern Ontario):  If you suspect that a child under the age of 18 years of age has measles, please page the infectious diseases physician on call at CHEO (613-737-7600, ext 0) to discuss the symptoms and determine if the child meets the clinical criteria and requires testing.  Clinically compatible signs and symptoms include all of the following:  fever (>38.3o orally), cough, coryza or conjunctivitis, and generalized maculopapular rash for at least 3 days.
  • Community laboratory:  The suspect case should ideally wear a surgical/procedure mask and be seen immediately upon arrival at the laboratory to reduce the risk of transmission to susceptible persons in the laboratory.

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