TORONTO -- The United States has joined a growing list of countries screening air travellers from China for a new virus linked to two deaths and dozens of infections, but Canada is so far not taking the same step.

Public Health Agency of Canada confirmed Friday that airports in Toronto, Montreal and Vancouver are rolling out new messages on arrival screens asking travellers from Wuhan -- the central Chinese city where the illness is believed to have started -- to contact a border service agent if they are experiencing flu-like symptoms.

If a traveller steps forward and shows signs of an infectious disease, they are then screened by a specially trained quarantine officer who can identify whether or not the passenger’s condition presents a potential public health risk.

Electronic kiosks at the three airports will also include an additional health screening question.

“Entry screening alone is not a guarantee against the possible importation of this new virus but is an important public health tool during periods of uncertainty and part of a multilayered government response strategy,” Public Health said in a statement, adding that the overall risk to Canadians is still considered low.

In the United States, 100 staffers from the Centers for Disease Control and Prevention have been dispatched to three airports: New York City's John F. Kennedy International airport, Los Angeles International Airport and San Francisco International Airport.

An estimated 5,000 travellers to the U.S. from Wuhan are expected to be screened in the coming weeks. Officials will use thermal scanners that can be pointed at travellers’ foreheads or temples for signs of illness, and travellers will be asked to fill out questionnaires asking if they visited meat or seafood markets in Wuhan.

Similar screenings are underway at airports in Japan and Thailand.

Canada does not have any direct flights from Wuhan, whereas New York and San Francisco each receive three flights per week from the city in central China. Los Angeles also receives a large number of travellers from Wuhan via Beijing.

The U.S. approach is meant to detect the virus early, says Dr. Nancy Messonnier, director of the U.S. National Center for Immunization and Respiratory Diseases.

“The earlier we detect this virus, the better we'll understand it, and the better we'll be able to protect people,” Dr. Messonnier said.

But whether or not airport screenings effectively prevent the spread of infectious illnesses is up for debate. The last time the U.S. ordered airport screenings was in 2014 due to concerns about the Ebola virus, and a passenger who was infected but did not show any symptoms passed through screenings.

Dr. Isaac Bogoch, a clinician investigator with the Toronto General Hospital Research Institute, described Canada’s approach as “balanced and measured.”

“These screening measures are typically not that efficient in picking up travellers because many people can be incubating the infection during the time of travel and are not actively sick,” he told CTV News.

Dr. Kamran Khan, a University of Toronto researcher who has studied airport screenings during the SARS and Ebola outbreaks, said airport screenings are far from foolproof.

"It's not a particularly effective intervention, and it potentially offers a false sense of security," Dr. Khan told The Associated Press.

A new report published Friday used modeling and estimated that the 45 confirmed cases in Wuhan could be grossly underrepresented. Researchers estimated that the number of cases in China could be as high as 1,723.

“It is certainly possible that this virus is more widespread within China and the reason we don’t know about it is because people just aren't sick enough to come to medical attention,” said Dr. Bogoch.

Concerns about the illness began earlier this month when multiple vendors from a fish market in Wuhan fell ill with the then-unknown virus. More than 40 cases have since been confirmed in China, with three cases in Japan and Thailand.

Two fatalities were reported, both in men over 60 with pre-existing conditions.

Chinese scientists have identified the virus’s genetic sequence and shared it widely, a step that the World Health Organization described as “of great importance.”

Symptoms of the coronavirus include fever, with a few cases involving difficulty breathing. Officials say the illness is likely spread through contact with animals, but have not been able to rule out the possibility of human-to-human contact as a factor.

Complicating matters is the fact that the new coronavirus shares symptoms with the common flu. Canadian public health officials say they will monitor the situation and take more aggressive measures if necessary.

With files from The Associated Press