Some travellers through Toronto's Pearson International Airport last month may have been exposed to measles.
Public health authorities are concerned in light of a confirmed case of the illness.
They say people in Terminal 1 on Sunday Jan. 27 from 4 p.m. to 8 p.m. may be at risk.
Those who were near people arriving aboard a Lufthansa flight -- LH-470 -- from Frankfurt at 4:08 p.m. may also have been exposed.
Also at risk are those connected to Air Canada flight AC-834 or LH-6829 that left Toronto at 6 p.m. for Montreal.
Authorities urge anyone who may have been exposed to check immunization records and watch for measles symptoms.
Symptoms, which can take up to 21 days after exposure to appear, include high fever, cold-like symptoms, sore eyes or sensitivity to light, and small spots with a white centre on the inside of the mouth, and a red rash lasting four to seven days