Canada, which has so far reported six cases of swine flu linked to the Mexican outbreak, Monday tightened airport screening for home-bound passengers and farm workers coming from Mexico.
Immigration Minister Jason Kenney said the measures were needed to check the spread of the swine flu which originated in Mexico, killing 149 people so far.
Each year more than a million Canadian tourists visit Mexico, while thousands of Mexicans come as temporary farm workers in Canada. The minister said each Mexican worker will be checked for fever by two doctors.
They will also be required to fill out a questionnaire and undergo medical check-up before entering Canada, he said.
"We think we've taken robust measures in co-operation with Mexican authorities to protect the health of Canadians," Kenney told the Canadian Press news agency.
"Someone who comes to work here - for any period of time - needs a medical exam just before departing," he said.
Currently, only those workers and students who stay here longer than six months are required to undergo a medical test. But now each of about 20,000 Mexican workers likely to come will undergo the medical screening.
Since all the six swine flu cases detected in Canada have shown only mild symptoms, Canada's top public health officer David Butler-Jones cautioned Monday: "Simply because we are seeing mild symptoms so far, does not mean we can take this for granted."
He warned, "We will likely see more severe illnesses and we will likely, unfortunately, see some deaths as well. We hope not, but that is a normal part of an influenza outbreak of any type."
Canadian Health Minister Leona Aglukkaq said, "The federal government has taken additional steps to protect travellers and has issued a health alert notice to the airlines that they are now distributing."
She said, "In addition, airlines are making onboard announcements to advise travelers of health precautions. The situation is evolving and we will remain vigilant and continue to monitor the situation closely."