“We must be prepared for the worst,” the health minister told reporters at the opening of the government’s Central Epidemic Command Center.

On Monday, Yeh said the threat was comparable to a tropical low-pressure area. But on Tuesday, he said the flu virus had already turned into a typhoon. “Will it reach Taiwan? Yes, it will blow all over the world,” Yeh said.

The change in the Cabinet official’s description followed an announcement from the World Health Organization Tuesday raising its global pandemic flu alert from level 3 to level 4, confirming there had been a sustained human-to-human transmission of the flu.

Yeh said the public should be cautious, but there was no reason for panic buying. “Taiwan has enough masks and drugs,” Yeh told reporters at the opening of a Central Epidemic Command Center. The department had more than 50 million masks in reserve, and manufacturers were ramping up production, he said, adding that exports could also be restricted if need be.

Taiwanese manufacturers had the capability of producing 200,000 doses of flu vaccine a month, while enough Tamiflu, the main drug used to treat SARS and other flu-like viruses, had been stockpiled to treat 2.3 million people, Yeh said.

Chen Chien-jen, who headed the Department of Health during the SARS outbreak in 2003, said Taiwan was the best prepared country in Asia, but expressed fears that it would be difficult to produce vaccines fast enough once the virus hit the country.

The CDC chairman from the SARS era, Su I-jen, predicted there would be a major outbreak in Taiwan within three to six months. He described the current cases as the first wave of the epidemic.

Chen opined late autumn could be the most dangerous time because it was the peak period for the traditional flu cases.

The government announced new checks on flights from the United States and Canada Tuesday, while cautioning against panic in the face of the growing threat from the H1N1 swine flu virus.

Beginning Wednesday morning, passengers on all flights arriving from the United States would have to wait on board until health officials had checked potential patients on the flight before being allowed to disembark, the Centers for Disease Control announced Tuesday.

The new measure was expected to affect more than 20 flights a day, reports said. Taiwan has no direct passenger air links with Mexico.

No cases of H1N1 had been recorded in Taiwan, while five people on Tuesday and one on Monday were ruled out as swine flu virus cases, CDC spokesman Shih Wen-yi said.

Anyone arriving at airports with fever higher than 37.5 degrees is checked and has to fill out a form, reports said.

Cable stations showed footage of a four-year-old Taiwanese boy returning with his family from Seattle being stopped at Taiwan Taoyuan International Airport because a screening machine showed he had high fever. The boy did not have the virus, but his family was told to keep his condition under close scrutiny.

Later Tuesday, there were also reports of a five-year-old boy returning from South Korea with a 38 degree fever.

Premier Liu Chao-shiuan linked the H1N1 threat with Taiwan’s long-time campaign to join the World Health Organization. The country wants to overcome China’s objections and obtain the status of observer at next month’s session of the World Health Assembly in Geneva. Taiwan insists it needs to so it can be more effective at combating international health threats such as SARS, bird flu and swine flu. Liu was speaking during an inspection of anti-flu measures at Taiwan Taoyuan International Airport Tuesday morning.

The opposition Democratic Progressive Party called on President Ma Ying-jeou to intervene in the fight against the virus and mobilize the National Security Council. The present administration could learn a lot from the past DPP government’s response to SARS, opposition lawmakers said.

The Taipei City Government ordered the Hoping Hospital, which had been cut off from the outside world during an outbreak of SARS in 2003, to serve as the capital’s H1N1 emergency center. The hospital presented its eight quarantine rooms to the media Tuesday. If necessary, the hospital could mobilize more beds, director Chu Ta-cheng told reporters.

Apart from airports, the country’s harbors were also upgrading their measures to try and stop the swine flu virus from entering Taiwan.

The port of Kaohsiung, one of the busiest container harbors in the world, formed an emergency response center Tuesday, while showing its isolation wards to the media. Crew members disembarking from ships would be checked for fever, officials said.

Government officials visited the outlying island of Kinmen to view its anti-virus control measures. The island lies close to the Chinese province of Kinmen and handles significant tourist traffic between China and Taiwan.