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Health Professionals Update - Vol. 18, No. 6

February 19, 2025

From: 
Monica Hau, MD, MSc, CCFP, FRCPC
Associate Medical Officer of Health

In this issue:

  • Increased measles activity in Southwestern Ontario
  • Measles prevention and preparedness

Key messages:

  • Southwestern Ontario is experiencing a measles outbreak.
  • Ensure patients are up-to-date with vaccinations, especially those planning travel, including infants six months and older.
  • Ensure all office staff are up-to-date with measles vaccination.
  • Include measles in differential diagnoses, particularly in symptomatic returning travelers.
  • Report suspected cases of measles immediately to Peel Public Health at 905-799-7700.

Increased measles activity

Measles cases are on the rise in Ontario due to rising global measles activity, reduced vaccination rates and increased international travel. In 2025, Peel Region has had one confirmed case of measles connected to international travel. In addition, Southwestern Ontario is currently experiencing a measles outbreak in connection to outbreaks in New Brunswick and Manitoba. While international travel was the initial source of the outbreak, all individuals with recent measles infections were exposed to the virus in Canada.

As of February 12, 2025, 99 cases of measles (67 confirmed, 32 probable) in Ontario have been connected to the outbreak. Outbreak cases have occurred in four public health units: Southwestern Public Health, Grey Bruce Health Unit, Grand Erie Public Health (formerly Brant County Health Unit and Haldimand Norfolk Health Unit) and Chatham-Kent Public Health. Eighty-four cases have been in children and adolescents, 98.8% of whom were unimmunized. More information can be found in Public Health Ontario's regular measles epidemiologic summary.

Vaccination remains the most effective way to prevent transmission. Health care providers should review and update patients' immunization status, particularly before March break, and any upcoming travel.

Up-to-date travel advice and destination-specific information is available on the Government of Canada website.

Measles prevention and preparedness

MMR eligibility

Ontarians may be eligible for up to two publicly funded doses of MMR based on the healthcare provider's clinical judgment and the needs of the patient.

Health care providers are encouraged to:

  • Ensure patients are up-to-date with measles vaccination and offer to eligible patients. Vaccination is preferred over serology when immunization status is unclear.
  • Ensure all office clinic staff are up-to-date with measles vaccination. All office clinic staff should have two doses of documented measles vaccination OR documented laboratory evidence of immunity. This includes staff members born prior to 1970.
  • Staff without two doses of documented measles vaccination or proof of immunity need to be excluded from clinical settings for up to 21 days from a measles exposure.

MMR vaccine can be ordered on the Health Professional's Portal.

MMR vaccine recommendations

Infants and children with planned travel

  • MMR can be given as young as 6 months of age. Two additional doses are still required after the first birthday at appropriate intervals.
  • Consider giving the second dose of MMR earlier than 4-6 years of age. Second dose of monovalent varicella vaccine is still required at 4-6 years of age.

Infants and children with no planned travel

  • First dose: MMR on or after the first birthday.
  • Second dose: MMRV at 4-6 years of age. If possible, give second dose of MMRV closer to age 4.

Individuals born in 1970 or later

  • If immunization status is unknown, two doses of MMR given at least 28 days apart.
  • If client only had one dose of MMR, give a second dose.
  • If client has two documented doses of MMR, consider fully immunized.

Individuals born before 1970

  • Considered to have natural immunity, however, some individuals may be susceptible.
  • Healthcare workers must have proof of immunity (record of two doses of MMR vaccine or serology).
  • Post-secondary students and travelers should consider getting at least one dose of MMR vaccine.

Clinical features of measles

Health care providers should consider measles in their differential diagnoses, especially for returning travelers with symptoms such as:

  • Fever
  • Cough, coryza or conjunctivitis
  • Generalized maculopapular rash starting 3-7 days after fever and respiratory symptoms

Advise suspect or confirmed measles cases to stay home from work, school, and other activities for four days after onset of rash.

Laboratory diagnosis

Testing for individuals suspected of having measles, including those who have a clinical syndrome and history compatible with measles (e.g., travel or exposure to a case) should include:

  • Measles virus detection by Polymerase Chain Reaction (PCR) (Nasopharyngeal/viral throat swab and urine) 
    and
  • Diagnostic serology (acute [IgM] and convalescent [IgG]).

Laboratory requisitions should be labelled "suspect measles" and include travel and vaccination status. Serology alone is generally not sufficient for diagnosis. Additional testing and specimen information can be found on the Public Health Ontario Laboratory website.

Infection control precautions

To reduce the risk of measles exposure to patients and staff, healthcare providers should follow these guidelines:

  • Ensure that all staff are adequately immunized against measles. Only immune staff should care for patients suspected of having measles.
  • A patient suspected to have measles should wear a surgical mask and ideally be placed on airborne precautions, or if not possible, in a separate room immediately upon arrival.
  • Suspected measles patients should call clinics in advance so that arrangements can be made to minimize exposures, such as booking at the end of the day.
  • After assessing a patient suspected of having measles keep the door closed and do not use the exam room for at least two hours.

Additional resources related to Measles immunization, laboratory testing and infection prevention and control practices are available on the Public Health Ontario website.

Reporting requirements

Measles is a reportable disease under the Health Protection and Promotion Act. Report suspected cases of measles immediately to Peel Public Health at 905-799-7700. Do not wait for laboratory confirmation.

Public health units will follow up with all measles cases and contacts to advise on isolation and post-exposure prophylaxis.

Contact us

The Health Professionals Update (HPU) is distributed to physician offices in Peel region via fax or email. Share this update with other health professionals in your clinic.

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