Mumps has made an appearance in Ontario after migrating from the Maritimes, where an outbreak has affected more than 200 people.
Canada usually has about 80 cases in the entire country in any given year.
Three mumps cases are confirmed in Ontario and five are suspected, and public health officials have warned the numbers are likely to increase as university students in Halifax finish up the year and return home.
"I would suspect this just reflects the tip of the iceberg, and there are a lot of other cases out there. We are still getting positive cases every day," said Dr. Todd Hatchette of the Halifax Medical Centre.
Nova Scotia has been the epicentre of the outbreak, and health officials are looking at a possible catch-up vaccination campaign for university students and health-care workers.
Such a vaccination program would give a second dose of the vaccine that covers measles, mumps and rubella vaccine to young adults as a follow up to the single childhood vaccine.
But the province has previously said the program would have to be done in co-operation with other provinces and territories.
In Nova Scotia the outbreak has spread to several health workers in the province who have been caring for mumps patients, and this week the number of those infected jumped from 157 to 203.
Mumps has been reported in all health regions of the province. In New Brunswick, there were 34 reported cases on Friday, and one in Prince Edward Island.
The three confirmed cases in Ontario are located in the Ottawa, York and Waterloo public health units -- and all can be directly linked to the Nova Scotia outbreak, said David Jensen, a spokesperson for Ontario's Ministry of Health and Long Term Care.
He said results are still pending on the five suspected cases.
Students especially vulnerable
University dormitories provide ideal conditions for the virus to flourish among young adults who are living in close proximity to one another.
It is easily spread through sneezing, coughing, kissing or any exchange of saliva, such as sharing food, drinks or cigarettes with someone who has the virus.
Mumps typically has an incubation period of 12 to 25 days. "You can have the mumps virus and not actually start having the symptoms until a couple of weeks later," said Dr. Mark Fletcher, medical director for a walk-in clinic.
Symptoms include aches, pains, fever, loss of appetite, and dramatically swollen saliva glands which give mumps carriers a characteristic chubby-cheeked look.
The disease can lead to worrisome complications.
"The worst-case scenario would be that we have so many cases that we would start to see some of the rare but feared complications of mumps -- deafness, meningitis and infertility," said Dr. Neil Rau, an infectious diseases specialist in Toronto.
Vaccination against mumps began in Canada in the 1970s. Since the 1990s, children in most jurisdictions get two shots.
Doctors say those who have only had one vaccination or have never been exposed to the disease could be at risk.
"If we don't have a good public health response, the small, vulnerable age group of of people who received only one dose of vaccine, might need to be chased after to get a second dose," Rau said.
Doctors want Canadians to check their vaccination records to ensure this outbreak doesn't worsen.
With a report from CTV's Denelle Balfour and files from The Canadian Press
