Measles is a highly contagious respiratory virus that lives in the nose and throat mucus of an infected person. It spreads easily from an infected person to others who are not immune to the virus. Individuals with measles spread the virus by coughing or sneezing into the air. It can also be transmitted when a person touches an infected surface and then touches their eyes, nose, or mouth.

The measles virus can live for up to two hours in the air or on a surface after an infected person leaves the area.

A person infected with measles typically begins to experience symptoms seven to 21 days after exposure. Symptoms can include a high fever, cold-like symptoms (cough/runny nose), sore eyes, and sensitivity to light. About three to seven days after symptoms begin, a rash typically appears.

The rash looks like red spots and blotchy patches that start on the face and then spread down the body, arms, and legs.

Some people with measles may suffer from severe complications, such as pneumonia (infection of the lungs) and encephalitis (swelling of the brain). Measles is especially dangerous to babies and young children as well as people with weakened immune systems. Complications of measles occur in about 10% of cases.

Vaccination is the best defence against measles. The efficacy of a single dose of a measles-containing vaccine is estimated to be 85% to 95%. With a second dose, efficacy is almost 100%.

Two doses of a measles-containing vaccine provide very high levels of protection against the virus and immunity is usually lifelong.

It’s important to note that more than 90% of people who are not immune to measles and who come into contact with the virus will become infected. That’s how contagious measles is and highlights the importance of being adequately protected against the virus.

The measles vaccine is available as a measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine.

Babies should receive the MMR vaccine at one year of age. Children should receive a second dose of a measles-containing vaccine, available as the MMRV vaccine, between the ages of four and six.

These vaccines are part of Ontario’s publicly funded vaccine schedule. The measles vaccine is required for children to attend school or a daycare centre in Ontario, unless they have a valid exemption.

Vaccination is also publicly funded for adults, if they have never had measles or been vaccinated.

Adults born before 1970 are generally presumed to have acquired natural immunity to measles; however, susceptible healthcare workers, travellers to destinations outside of Canada, and military personnel should receive an MMR vaccine, regardless of year of birth.

In addition, the Ministry of Health advised Grey Bruce Public Health in early May 2025 to implement the following measles outbreak immunization strategy. This expanded eligibility for the MMR vaccine pertains to individuals who live or work in or who will be travelling to or spending time in Grey-Bruce.

• Infants (aged 6-11 months) should receive one dose of the MMR vaccine. Two additional doses will still be required after the age of one year.
• Children (aged one to four years) who have received their first dose of MMR vaccine are encouraged to receive a second dose as soon as possible (at a minimum of four weeks from the first dose).
• For Adults (18+ years) born on or after 1970, a second dose of the MMR vaccine is recommended.

If you are unsure about your vaccination status, you can check ICON, contact the Health Unit where you would have received your immunizations, or talk with your doctor. For those who are still unsure if they are immune or not, a blood test may be ordered, or they may consider talking with their doctor about whether they should receive a dose of vaccine.

People can be infectious with measles for four days before to four days after the measles rash develops. If an individual develops measles symptoms, they should immediately isolate at home and call a healthcare provider. Household members who are not immune to measles should also stay home during this period and consult with public health.  

Before going to a healthcare facility, such as a hospital or physician’s office, the individual must ensure the facility knows that they may have measles so the facility can take appropriate precautions as soon as the person arrives to prevent the virus from spreading to others.

Individuals who suspect they have measles are advised to not go to a healthcare facility or office without calling ahead first.

If there is a known case of measles in the community, public health will follow up to determine who is most at risk of being exposed to the virus. Public Health (or designate) will notify all individuals associated with the exposure to the best of their ability. This includes people who were exposed at a health care facility, school, workplace, etc.

• Confirm vaccination status. Ensure all individuals in the household are up to date on measles vaccination. In general, those born before 1970 are considered immune against measles. Two doses of a measles-containing vaccine are recommended for anyone born after 1970. If unsure of vaccination status, individuals should check with their healthcare provider or ICON
• If not protected against measles, individuals should contact their healthcare provider or GBPH, and avoid contact with pregnant individuals, young children, and others with weakened immune systems.
• Monitor for measles symptoms, which generally start 7 to 21 days after exposure. Symptoms can include high fever, cold-like symptoms (cough/runny nose), sore eyes, and sensitivity to light. About three to seven days after symptoms begin, a rash typically appears. The rash looks like red spots and blotchy patches that start on the face then spread down the body, arms and legs.
• If measles symptoms develop, immediately isolate at home and call a healthcare provider. Household members who are not immune to measles should also stay home during this period and consult with public health. If medical care is required, call ahead to a healthcare facility before arriving in-person, so the facility can take precautions to prevent the virus from spreading to others.
• Special Note for Health Care Workers and Military Personnel: If you are a health care worker or military personnel, please consult with your employer regarding expectations for immunization or proof of immunity to measles.