Asean said member states were "better prepared now following the experience from recent Sars (severe acute respiratory syndrome) and avian influenza outbreaks" that killed hundreds of people.
Asean says it has a stockpile of one million courses of Tamiflu and Relenza, anti-viral drugs used during the bird flu and Sars outbreaks, in a region with a population of 560 million people.
According to international health officials a specific vaccine for swine flu does not exist yet.
Meanwhile in New Zealand, officials reduced the number of confirmed or probable swine flu cases by one to 13, after further checks showed a woman believed to have travelled from Los Angeles had in fact come from Samoa.
Tony Ryall, New Zealand's health minister, said the government was treating 13 other people as "confirmed cases" although laboratory tests confirmed the H1N1 virus in just three people.
He said the number of suspected swine flu cases more than tripled from 31 on Wednesday to 104 on Thursday.
"The growth in the suspects is primarily from close family contacts of passengers on flights," Ryall told reporters.
"We are working hard to identify people potentially with swine flu so that we can provide them with treatment and support and limit the spread of the flu."
Australia was also testing more than 100 people with flu symptoms for the virus as the government granted health authorities wide powers to contain contagious diseases.
Eight confirmed in Mexico and 151 suspected. One death in the United States
Countries with confirmed cases: Mexico, the US, Canada, New Zealand, Spain, Israel, Britain, Germany, Austria, Switzerland, Netherlands, Costa Rica
Countries with suspected cases: Australia, Brazil, France, Chile, Denmark, Colombia, Germany, Norway, South Korea, Guatemala
Annual influenza epidemics are thought to result in three to five million cases of severe illness and between 250,000 and 500,000 deaths around the world, WHO says.
Thermal scanners were in place in several Asian countries checking passengers arriving from North America, and doctors were going on board arriving flights in Japan and Taiwan looking for signs of fever.
Malaysian officials said the government has multi-strain flu vaccines for two million people, and would administer some of that to 200,000 doctors, nurses, police and immigration officials who might have first contact with the virus.
In the Philippines, dozens of legislators were asked to abandon plans to visit Las Vegas to cheer for boxing idol Manny Pacquiao.
And in China, the government has had to fend off suggestions that the disease could have originated in the country, saying no such virus had been detected there.
China, which has been the source of other flu strains in the past, said the claims were groundless and aimed at tarnishing its image.
Mao Qunan, a spokesman for the health ministry, said the allegations were "driven by ulterior motives" aimed at adding confusion.
"Some overseas media have ignored the facts of the epidemic and basic scientific knowledge and deliberately fabricated rumours that this epidemic came from China," he said on the ministry's website.
"[They] aim to muddle right and wrong, create disturbances and ruin China's image. We are resolutely opposed to this."