Asia tightened its already strict measures to keep swine flu from spreading across the region on Tuesday, after the World Health Organisation warned of a significant increase in the risk of a pandemic.
The number of suspected cases across the region jumped, with New Zealand investigating 56 possible new infections, Australia 17 and South Korea a single case among people who had recently returned from Mexico or the United States.
Nine New Zealand high school students and their teacher had already tested positive for influenza A and were thought likely to have contracted swine flu. Tests results were expected later this week.
"It's a time for caution and concern, but not alarm," said New Zealand Health Minister Tony Ryall. Three suspected cases from a separate New Zealand school group that visited Mexico had tested negative.
But officials were still trying to trace 18 people who arrived on the same flight from Los Angeles as the main group of school children.
In neighbouring Australia, health authorities said they were investigating 17 possible cases and health officials were put on high alert.
Health Minister Nicola Roxon said clinical staff had been stationed at all international airports, while airlines operating from the Americas were required to report the health status of passengers before landing.
Most countries in the region have already increased airport checks to screen passengers arriving from affected areas and advised against non-essential travel to Mexico, where the virus has killed a suspected 152 people.
Thermal scanners have been a common feature in many Asian airports since the Severe Acute Respiratory Syndrome (SARS) epidemic of 2003.
Japan went one step further, saying it would temporarily tighten visa restrictions for Mexican nationals as part of efforts to stop the virus entering the country and urged Japanese citizens in Mexico to return home.
It also booked 500 hotel rooms near Tokyo's Narita International Airport in case it needs them to quarantine infected travellers, Jiji Press reported.
The World Health Organization's Keiji Fukuda said a pandemic was not inevitable and that while the hike in its alert level was a "significant step towards pandemic influenza, it's also a phase which says we are not there yet".
If the world health body further increased its alert level, Japan would quarantine arrivals suspected of having the virus, as well as those who accompany them and flight attendants, for 10 days of tests, Jiji said.
Hong Kong, which was at the forefront of the SARS epidemic in 2003 and has since been on alert for bird flu, has already issued similar guidelines allowing for arrivals to be detained, as has Australia.
The first suspected case of the virus in East Asia was reported in a woman in South Korea just back from a trip to Mexico, health officials said.
Officials in Seoul said they would double stocks of Tamiflu and other anti-influenza drugs -- enough to treat five million people.
Countries including New Zealand have said contingency plans drawn up during the bird flu epidemic that reappeared in 2003 meant health authorities had plentiful stocks of anti-flu medication.
Local authorities were looking for any clusters of flu-like illness in India which, along with Thailand, said it was trying to track down an unknown number of people who had recently arrived from Mexico and the United States.
Health experts have expressed fears that the relatively low death rate and mild symptoms seen in some cases of the current strain could allow the virus to spread faster.
Taiwan's Health Minister Yeh Chin-chuan, who on Monday insisted there was no need to panic over the outbreak, which he described as a "a tropical storm emerging on the other side of the Pacific", updated his forecast.
The outbreak was "becoming a typhoon likely to approach us", he warned.