There are now 32 cases of measles in the Lanaudière region of Quebec, which is an increase of 13 cases since last week.
So far, all of the cases are linked to a member of a religious group who took a trip to Disneyland.
All those who have the illness are not vaccinated.
What exactly is measles?
Measles is a highly contagious infection that causes high fever, a distinctive rash and a runny nose.
Complications can include pneumonia, deafness and death in about one or two cases per 1,000 infected individuals.
It’s spread through direct contact, through the air when a person coughs or sneezes, and by touching objects that were recently exposed to infected mucus or saliva.
Measles can survive up to two hours in the air, even if the contagious person has left the space.
What are the risks?
Measles is one of the leading causes of death among young children worldwide, according to the World Health Organization, but it’s rare in Canada.
Since the introduction of a vaccine in the 1960s, the number of cases in Canada has declined dramatically.
There is no treatment for measles and most people recover within two to three weeks, though complications can arise.
The Public Health Agency of Canada recommends people drink lots of fluids, eat healthy foods and get plenty of rest.
How is it prevented?
Measles can be prevented with two doses of vaccine, including the measles-mumps-rubella (MMR) immunization or measles-mumps-rubella-varicella (MMRV) immunization.
In Quebec, the needle vaccine is given to children first at 12 months and then a booster is given at 18 months.
One dose of the vaccine isn’t sufficient to guard against the infection, health officials say.
In 2011, Quebec was hit with the biggest outbreak of measles in North America, recording nearly 700 cases. At that time, doctors said many of those cases were people who had not received the measles, mumps and rubella vaccine.
A major vaccination program was launched, but doctors said there are still parents who choose not to vaccinate their children.