What is Measles?
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.
How can measles be prevented?
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.
Who should receive the measles vaccine?
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.
Infants aged six to 11 months can receive a publicly funded dose of a measles-containing vaccine if they live or will be travelling to an area experiencing a measles outbreak.
How can I check my vaccination status?
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.
What should I do if I think I have measles?
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.
How will I know if I have been exposed to measles?
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.
What should I do if I’ve been exposed to measles?
Measles Exposures
Local community exposures to measles are included in the table below. Provincial measles exposure information is available here.
Resources for Healthcare Providers
Measles: Information for Health Care Providers – Public Health Ontario
Measles: Post Exposure Prophylaxis for Contacts – Public Health Ontario
Summary Recommendations: Measles Post-Exposure Prophylaxis for Individuals Who Are Immunocompromised Due to Disease or Therapy – Public Health Ontario
Measles IPAC Checklist for Clinics and Specimen Collection Centres – Public Health Ontario
Measles Vaccines: Canada Immunization Guide
Measles Information – Ontario College of Family Physicians
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