Two passengers on Air China flight CA991 from Beijing have tested positive for measles, prompting Vancouver Coastal Health to issue a public advisory.

Reka Gustafson​, VCH medical health officer, said the two passengers arrived in Vancouver on March 21 and would have been infectious on the flight.

"It was an astute family physician who called us suspecting measles," she said Monday night. "As soon as the tests came back positive, we alerted the public."

The health authority is also contacting passengers on the flight.

"We were able to get a flight manifest ... and a list of passengers who were sitting closest to the individuals infected and we've spent time trying to reach them, as well as flights crews," she said.

She added that while measles is rare in Canada, unimmunized people are at risk of contracting the viral infection. Passengers who are not up-to-date on their measles vaccinations should get the MMR vaccine as soon as possible, she said.

Individuals born before 1957 are considered immune and do not need a vaccine, but those born betwee‎n 1957 and 1970 should have one dose and those born after 1970, should have two doses of measles-containing vaccine.

Gustafson wouldn't say how the two infected passengers were connected or their ages, but she did say they were travelling together and live in the Lower Mainland.