Passengers from a recent BC Ferries sailing and students at a Maple Ridge high school are being warned that they might have been exposed to the highly contagious measles virus.

Fraser Health said someone suffering from measles took the 7 p.m. ferry from Tsawwassen to Mayne Island on Friday, Aug. 31, potentially infecting other travellers on the vessel.

“If you travelled on this ferry during this time period, check your immunization status," Medical Health Officer Dr. Ingrid Tyler said in a statement.

"If you develop any of the symptoms and have a fever, call your doctor and inform them that you may have been exposed."

The same infected individual then went to Maple Ridge Senior Secondary School the following Tuesday as students returned to classes after Labour Day.

Staff and students at the school have been urged to check their immunization status as well. To be fully protected from the disease, you must have had two doses of the measles-mumps-rubella vaccine.

Students and teachers who have never had a single dose of the vaccine in their lifetime have until Monday, Sept. 10 to get one – otherwise health officials have ordered that they not return to the school until Sept. 26.

"You are most at risk of measles infection if you are completely unvaccinated," Tyler said.

Babies are also particularly susceptible if they have never been infected with the disease before, Fraser Health said. People who were born before 1970 are less at risk than the rest of the population, as they are likely to have been infected already.

Measles has an incubation period of about 10 days, meaning people usually don't begin to show symptoms until more than a week after exposure to the disease. Fraser Health said it sometimes takes as long as 21 days.

Symptoms include fever, cough, runny nose and red eyes that leads to a rash that lasts at least three days. It can sometimes cause severe complications including brain inflammation, convulsions, deafness and brain damage.

Fatal infections are fairly rare in Canada, occurring only once in every 500-3,000 cases.

Anyone who is unsure about their immunization status is advised to call their doctor for advice.