Measles is a virus of the family Paramyxoviridae that is spread via the airborne route and also through coughing, sneezing and direct contact with respiratory secretions. It is one of the most infectious viruses known with a reproductive rate of 12 to 18 per cent in fully susceptible populations.

Measles infection is uncommon in Toronto with a five year average of three cases per year reported to Toronto Public Health (TPH). Most of these cases are the direct result of travel. However, from time to time, local outbreaks of measles infection occur.

In Ontario, one dose of a combined Measles, Mumps, Rubella (MMR) vaccine is currently given on or after the first birthday followed by a second dose at four to six years as MMRV (combination vaccine – MMR with varicella). Most schools have vaccination rates of 90 per cent or more.

A cohort of individuals born between 1970 and 1992 may not have received two doses of the MMR vaccine. Those born before 1970 likely had natural infection and are considered immune (except for health care workers who are not considered immune by age and require either proof of two doses of vaccine or serology showing measles immunity).

Clinically compatible signs and symptoms are characterized by all of the following:

  • fever ≥ 38.3 degrees Celsius (oral)
  • cough, coryza or conjunctivitis
  • generalized maculopapular rash for at least three days

Most cases of measles become apparent 10-14 days after contact with the virus. Incubation period ranges from seven to 21 days. Exclusion for measles exposure begins five days after first exposure due to the possibility of transmission in some cases before the prodrome. Cases are infectious from four days before to four days after rash onset.

Diagnostic laboratory testing is indicated for individuals who have a clinical syndrome and history compatible with measles (e.g., travel or exposure to a case) and should include both measles virus detection by poly chain reaction (PCR) (nasopharyngeal/ throat swab and urine) and diagnostic serology (acute and convalescent).

Important: specimen documentation and transport

On each laboratory requisition for virus detection (PCR) or diagnostic serology clearly mark “suspect case of measles.” All requisitions should contain the following information: patient’s symptoms, date of onset of symptoms, exposure history, travel history (if any) and vaccination history. The diagnostic tick box should also be marked. Specimens must be stored and shipped cold.

Measles virus detection by PCR

  • A nasopharyngeal swab/aspirate or throat swab collected using Viral Transport Media (pink liquid medium) obtained as soon as possible and within seven days after rash onset and
  • Approximately 50 mL of urine collected within 14 days after the onset of rash.

Note: A negative PCR should not be used to rule out measles and needs to be interpreted along with serology, symptoms, exposure history and vaccination status. In certain situations, such as when there is a high index of suspicion for measles (e.g., compatible illness in a returned traveller or contact of a laboratory-confirmed case) it may be warranted to test beyond the above time periods when specimens could not be collected earlier in the illness. This can be discussed with Toronto Public Health (TPH) on a case by case basis.

Diagnostic serology

Acute serology

  • A blood specimen (5ml in serum tube) for measles antibodies (IgM and IgG) collected at the first visit (ideally within seven days after rash onset). The requisition should be clearly marked “acute measles serology”.

Convalescent serology

  • A second blood specimen collected seven to 10 days after the onset of rash (and a minimum of five days after the acute sample). The requisition should state “convalescent measles serology”.

Interpretation of serological results

IgG seroconversion (patient moving from IgG negative to IgG positive), or a significant rise in IgG (four-fold increase) is indicative of recent/acute infection.

Detection of IgM indicates acute infection in a person who is either epidemiologically linked to a laboratory-confirmed case or has recently travelled to an area of known measles activity. However, in a low prevalence setting such as Canada, IgM detection may also be due to a false-positive result due to assay non-specificity. Further testing is required to conclude that the patient has measles.

Note: Diagnostic laboratory testing on well persons who have recently received measles-containing vaccine as part of the routine schedule or in advance of planned travel is not indicated.

Contact the Public Health Ontario (PHO) Laboratories customer service at 416-235-6556 or 1-877-604-4567 if you have any questions or contact TPH at 416-338-7600.

More information:

  • Two doses of Measles, Mumps, Rubella (MMR) vaccine are recommended for all individuals born on or after 1970 in Toronto based on local epidemiology.
  • For children initiating their vaccination schedule, the first dose should be given on or after the first birthday. The second dose, now given as Measles, Mumps, Rubella and Varicella (MMRV), should be given between four to six years of age or at least 28 days after the first dose.
  • If an individual is unsure of their vaccination history, provide a dose of MMR vaccine.

Infants less than one years of age

  • Infants six months of age or older who may be travelling to measles endemic countries can get a dose of MMR vaccine, but will still require two doses after the first birthday.

Health care settings

For prevention of measles transmission in healthcare settings, all employees (e.g., nurses, physicians, support staff) should ensure that they are immune to measles. In the event of a measles exposure, employees will be excluded from work from five to 21 days post measles exposure unless they can provide proof of immunity regardless of their year of birth. Proof of measles immunity includes:

  • documentation of receipt of two doses of measles-containing vaccine on or after the first birthday, with doses give at least four weeks apart, or
  • laboratory evidence of immunity

More information

Summary of updated measles post-exposure prophylaxis (PEP) recommendations for susceptible contacts

Population Time since exposure to measles ≤ 72 hours Time since exposure to measles 73 hours – six days
Susceptible infants zero to six months of age IMIg (0.5 mL/kg) IMIg (0.5 mL/kg)
Susceptible immunocompetent infants six to 12 months of age MMR vaccine IMIg (0.5 mL/kg)
Susceptible immunocompetent individuals 12 months of age and older MMR vaccine series MMR vaccine series
Susceptible pregnant individuals IVIg (400 mg/kg)
IMIg (0.5 mL/kg), limited protection if 30kg or more
IVIg (400 mg/kg)
IMIg (0.5 mL/kg), limited protection if 30 kg or more
Susceptible immunocompromised individuals six months of age and older IVIg (400 mg/kg)
IMIg (0.5 mL/kg), limited protection if 30kg or more
IVIg (400 mg/kg)
IMIg (0.5 mL/kg), limited protection if 30 kg or more
Individuals with confirmed measles immunity No PEP required No PEP required

Reference and more information

Canadian Communicable Disease Report: Updated NACI recommendation for measles post-exposure prophylaxis (Public Health Agency of Canada)

Airborne precautions are used in addition to Routine Practices for patients known or suspected of having measles. (Additional personal protective equipment (PPE) such as gloves and gowns may be added as required based on risk assessment as per Routine Practices.)

In a clinical office setting, follow Provincial Infectious Diseases Advisory Committee’s (PIDAC) Infection Prevention and Control for the Clinical Office Practice

  • Make every effort to see the patient at the end of the day, if clinical status allows.
  • Quickly triage the patient out of the common waiting areas and move the patient to an examining room. If possible, the patient should enter and exit through a separate entrance and go directly in and out of the examination room.
  • Provide a surgical face mask for the patient to wear at all times while in all areas of the clinical office. For practices with a large pediatric component, pediatric masks are now available for purchase.
  • Keep the door to the treatment/exam room closed. Visitors and staff should not enter the room unless they are immune to measles. Open a window in the room, if this is possible.
  • Place alert signage for staff on the closed door.
  • An N95 respirator is not necessary if the health care provider has documented immunity to measles infection. Only immune staff should provide care to patients with measles.
  • Allow sufficient time for the air to change in the room and be free of droplet nuclei before using the room for a non-immune patient (for measles). The time required may be minimized if the patient has worn a surgical mask consistently.
  • Routine cleaning for the room or equipment is sufficient after examining a patient under Airborne Precautions.

In an acute care setting, promptly isolate the patient with suspect or confirmed measles in a single room with negative air flow (airborne isolation room) and the door closed. Precautions should be in place for four days after the start of the rash and for the duration of illness in immunocompromised patients.

Patient movement should be curtailed unless absolutely necessary and then only conducted with the patient wearing a surgical mask.

More information

Routine Practices and Additional Precautions in All Health Care Settings (PIDAC)

  • There is no specific treatment for measles.
  • Medical care is supportive and to help relieve symptoms and address complications such as bacterial infections.

Call Toronto Public Health’s surveillance unit immediately at 416-392-7411 during business hours (8:30 a.m. to 4:30 p.m., Monday to Friday) or 311 after hours to report all suspect and confirmed cases of measles infection.