TORONTO 芒鈧珺次元官网网址� With the start of summer vacations just a few months away, the country's top doctor is urging Canadians to make sure their measles vaccinations are up to date, especially for those planning to travel overseas.

Dr. Theresa Tam, Canada's interim chief public health officer, said people who were not vaccinated or not exposed to measles as a child should arrange to get inoculated, while anyone who's unsure of their immunization status should check with their doctors.

Those who need to update their protection against the disease should get their shots six weeks before travelling, she said. 

"In Europe, there are a number of countries experiencing cases," said Tam, calling measles a highly contagious disease that continues to circulate in many parts of the world.

Romania, for instance, has reported almost 2,000 cases since February 2016. Measles has killed 17 children in the country, none of whom were vaccinated.

Vaccination rates have been falling in some central and eastern European countries, driven in part by an anti-vaccination movement whose messages have been taken up on social media.

Measles is caused by a virus that can rapidly spread through person-to-person contact, via droplets in the air when an infected person coughs or sneezes or by touching objects recently exposed to infected mucus or saliva.

While home-grown cases have been eliminated in Canada 芒鈧珺次元官网网址� the last domestically acquired case was in 1997 芒鈧珺次元官网网址� Canadians who are unvaccinated or under-vaccinated can still contract the disease through infected people who travel into this country, she said Monday.

That could mean an outbreak of measles if the virus takes hold within an undervaccinated population, as it did in 2015 in an area of Quebec, when almost 200 cases occurred after an infected visitor introduced the disease into the community.

"The introduction can cause little sparks," said Tam. "If you introduce that spark into a population that's underimmunized, that actually catches fire. It will cause a cluster or an outbreak of cases."

Tam said there have been 10 confirmed cases of measles in Canada so far this year 芒鈧珺次元官网网址� all related to travel 芒鈧珺次元官网网址� and a few suspected cases are under investigation.

Three of those cases, confirmed by Toronto Public Health last month, are connected to people who travelled to or within Canada on WestJet or Emirates Airline flights in the last two weeks of March.

"It's important to remember that measles has a long incubation period, up to 21 days, so we're still in the period of time when people who are exposed to these three confirmed cases may come down with measles," said Dr. Michael Finkelstein, associate medical officer of health for Toronto.

Initial symptoms include fever, cough, runny nose, red eyes and irritability. Small white spots may also appear inside the mouth and throat. Three to seven days later, a red blotchy rash develops on the face and spreads over the body.

Symptoms begin a week to three weeks after exposure to the virus and a person can spread the infection to others from four days before the rash starts until four days after its disappearance. The virus is most often spread when people first get sick or before they know they have measles.

"We're telling people to watch for signs and symptoms of measles if they were exposed," said Finkelstein. "If they should start to become ill, it's important for them to stay home."

Those who develop symptoms should seek medical attention, but call ahead before visiting their doctor, medical clinic or hospital emergency department so precautions can be taken to isolate them to prevent transmission to others, he said.

There is no specific treatment for measles and most people recover within two to three weeks. However, measles can be especially dangerous for infants and young children, and those with weakened immune systems.

"About 30 per cent of those who get measles will have some kind of complication, and they range from ear infections to pneumonia to more severe complications such as encephalitis, which is inflammation of the brain," said Tam. That swelling of the brain can cause seizures, brain damage and even death.

"So it is not a benign disease," she said.

The best way to prevent measles is to get inoculated with two doses of the measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) immunization. The initial shot is given to a child at 12 to 15 months of age, followed by a second dose between 18 months and four to six years of age.

Adults whose immunizations aren't up to date should receive at least one dose of the vaccine, although two is preferable as some people don't build up antibodies to the virus with a single dose, said Finkelstein.

Tam said having 95 per cent of a given population vaccinated is typically enough to provide protection from infection for those who haven't been immunized because of a phenomenon called "herd immunity" 芒鈧珺次元官网网址� which means the virus has difficulty spreading because there are too few hosts left to infect.

In Canada, about 90 per cent of two-year-olds and almost 86 per cent of seven-year-olds had been vaccinated against measles, according to the 2013 childhood National Immunization Coverage Survey.

"So there is a possibility of there being clusters or outbreaks as a result," Tam said.

Follow @SherylUbelacker on Twitter.

Sheryl Ubelacker, The Canadian Press

Note to readers: This is a corrected story. A previous version identified Tam's position as interim

chief medical officer of health.