Governments including China, Russia and Taiwan began planning to put anyone with symptoms of the deadly virus under quarantine. Other governments were increasing their screening of pigs and pork imports from the Americas or banning them outright.
Many nations issued travel warnings for Mexico.
Australia said airlines would have to identify passengers who may be infected, who would then be assessed by quarantine officers and sent for medical treatment if necessary.
“Before flights will be able to land here in Australia, pilots will have to ascertain whether anyone on board has flu-like symptoms,” Health Minister Nicola Roxon said.
Tests were also under way on people with flu-like symptoms in Israel, France and Spain.
In the United States, at least 11 cases of swine flu have been confirmed. Canada’s chief public health officer Dr. David Butler-Jones said six cases had been confirmed there, and all had links to people who had traveled to Mexico.
In Singapore, the health ministry said it began using thermal scanners Sunday at Changi International Airport to check passengers arriving from the United States. Travelers with high temperatures would be given a thorough medical examination, it said.
Thermal scanners and upgraded checks for flu-like symptoms were also being put in place at main airports in Japan, Thailand and Indonesia.
Hong Kong and Taiwan said visitors returning from flu-affected areas with fevers would be quarantined.
China said anyone experiencing flu-like symptoms within two weeks of arrival had to report to authorities.
A Russian health agency said passengers from North America running a fever would be quarantined until the cause is determined.
Many measures recalled those taken across Asia during the 2003 severe acute respiratory syndrome, or SARS, epidemic and used more recently to monitor bird flu.
Compared to the rest of the world, the United States seems to be slow to react to the outbreak.