The new H1N1 virus, apparently a mix of human, pig and bird viruses, is believed to have killed more than 100 people in Mexico, where it was first detected, and is suspected to have spread to different continents.
The World Health Organisation has warned of a possible pandemic as New Zealand, Australia, the US, Canada, Brazil, Spain and Israel joined the growing list of countries where confirmed or suspected cases have been reported.
Japan, Singapore, Malaysia and Indonesia said they were screening passengers at checkpoints for fever and flu symptoms, many using devices at airports that had been put in place to monitor Sars and bird flu over the last few years.
|Passengers are being screened at some airports for flu symptoms [Reuters]
Hong Kong raised its swine-flu response level from "alert" to "serious" and warned against travel to Mexico, as did South Korea.
Japanese authorities said there were plans to put up signs urging passengers going to Mexico to "wear masks, wash hands and gargle".
Health authorities in the Philippines, China and Taiwan began planning to put anyone with symptoms of the deadly virus under quarantine.
Francisco Duque, the Philippine health secretary, said the government was also blocking the entry of any pigs or pork products from Mexico and the US.