2. Measles is caused by a virus that spreads through the air
Measles is caused by the virus Human measles virus of the family of Paramyxoviridae. It is transmitted through the air (coughing, sneezing, droplets of saliva suspended in the air).
3. Measles is extremely contagious
The majority of respiratory viruses do not travel very far from the sick person, but for measles, it is different. “The measles virus is transmitted efficiently by fine particles that remain suspended in the atmosphere for hours,” explains Jesse Papenburg. This means that you can catch measles by going to a place where a sick person was previously, even if the person has since left the area.
The reproduction rate of the virus, called R0, is estimated between 12 and 16. This means that in an unvaccinated population, a person sick with measles will infect on average between 12 and 16 people.
“This is why measles is considered the most contagious infectious disease,” says the expert.
In contact with a sick person, a person who is not vaccinated or who has never contracted the virus has a 9 out of 10 chance of catching the disease.
Comparison between the different R0s. In this GIF, we see the number of people infected after 5 cycles of infections with three viruses having a different R0, namely the influenza virus, the respiratory syncytial virus (RSV) and the measles virus (measles). Credit: Kristen Panthagani
4. Measles can cause serious complications
A child with a rash caused by measles. Photo: CDC
-The symptoms at the very beginning of the disease are similar to those of other respiratory diseases, i.e. fever, runny nose, red eyes and cough. “You can thus become infected and transmit the disease without knowing that it is measles,” says Jesse Papenburg, doctor at the Montreal Children’s Hospital.
7 to 18 days after the infection begins, a characteristic rash (redness) appears on the face and rest of the body. “This is what tells the clinician that it is measles. The rash typically starts on the scalp and then moves down the rest of the body,” reports Dr Papenburg.
Although they occur rarely, measles can cause severe complications: acute otitis media, pneumonia, encephalitis (inflammation of the brain). Young children are the most vulnerable. Measles can even cause immune amnesia, meaning that the immune system is weakened and loses its ability to fight other viruses that it was capable of countering.
“Mortality risks are higher in developing countries, particularly in a context of malnutrition among children,” indicates Dr Jesse Papenburg. According to the World Health Organization, 107,500 people worldwide, mostly children under 5, died from measles in 2023.
5. Vaccinated people are well protected against measles
A fully vaccinated person, that is to say having received both doses, is protected throughout their life. Aside from the vaccine, the effectiveness of which is 95% after the 2e dose, there is no specific treatment. Complications resulting from the disease, which are often secondary bacterial infections, are treated.
The vaccine is offered free of charge across Canada.
6. Some people, such as unvaccinated babies, are more vulnerable to illness
- Babies and children who have not yet received the MMR vaccine (measles, mumps and rubella vaccine). According to the Quebec vaccination schedule, the first dose of the MMR vaccine is administered to children at the age of 1 year; the second at 18 months.
- People with a weakened immune system. Unvaccinated pregnant women. People who are not properly vaccinated against the disease. Unvaccinated people born after 1970. Those who were born in Quebec before 1970 and grew up in Quebec have, in general, already had measles and are possibly protected.
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