By Kate McGeown BBC News Online

Governments around the region have stepped up their entry requirements, some invoking tough new quarantine laws.

Visitors to Singapore are greeted by a team of health officials

Health workers have been stationed at several East Asian airports, checking arriving passengers for symptoms.

And airlines have cancelled flights to and from affected areas, leaving tourists and business travellers with the difficult decision of whether to risk visits to the region.

Tour companies are reporting huge losses and hotels in some areas are virtually empty.

On Wednesday, Malaysia became the first country to block the entry of visitors from certain areas altogether.

The Malaysian Embassy in Beijing announced it had stopped issuing tourist visas for travellers from mainland China and Hong Kong, with only members of the government and those on business trips eligible to apply.

While Hong Kong still insists that visitors from all areas are welcome, everyone arriving at the territory's international airport must now fill in a detailed health form, said Sally Kong, an information officer from the Department of Health.

Passengers departing from Hong Kong must also mention any symptoms of fever or history of contact with possible Sars cases before they can leave the country, the Department of Health said.

Travellers in Taiwan are taking extra precautions

The authorities in Bangkok have gone a step further - imposing strict quarantine rules on people entering Thailand.

All passengers arriving from affected areas are required by law to stay at home or in one place for 14 days after arrival.

Ticaya Laorakpong, a medical officer temporarily based at Bangkok's International Airport, said that every passenger arriving from Hong Kong, Taiwan, China, Vietnam and Singapore must be screened by health officials before entering the country.

"If we suspect anyone has the disease we conduct further tests such as chest X-rays," he told BBC News Online. "We did five X-rays on Tuesday."

"If we are still unsure, we will keep the person in for treatment for a further 24 days," he added.

Singapore has also stipulated that arriving passengers must fill in a health declaration form, and that anyone who has been in contact with an infected individual must be quarantined for 10 days.

Taiwan, too, has issued tough restrictions, banning civil servants from visiting China and other affected areas.

And the authorities in Australia have announced new powers allowing them to forcibly quarantine those suspected of suffering from the potentially deadly virus.

Staying at home

Safety concerns and strict restrictions are prompting many potential business travellers to stay at home.

Southeast Asian finance ministers have said they might postpone an upcoming meeting in Manila, while Norwegian mediators are considering shifting peace talks between the Sri Lankan Government and Tamil Tiger rebels away from Thailand.

Mel Capper, a spokeswoman for Lonely Planet travel guides, said that tourists planning trips to the region were also concerned.

Passengers arriving in Bangkok are being routinely screened

The Lonely Planet's internet bulletin board was full of questions from travellers planning to visit East Asia, she said.

"People are asking if they should reconsider their trip even if it is planned for a few months away," she added.

While no one was panicking, there was concern about the disease, as well as the prospect of travellers being stuck in a country because of legal quarantine periods, Ms Capper said.

Tour companies and airlines in the region are seeing dramatic cuts in business, already hit by worries about the war in Iraq.

Airlines cancelled more than 30% of their services in and out of Hong Kong International Airport on Wednesday, the airport authority said.

Some of the territory's five-star hotels are reported to have occupancy rates of just 10%.

An official for Thai Airways said the airline's bookings for May were down by 15% from last year due to major cancellations, particularly on routes to Hong Kong, Singapore and other areas affected by Sars.

"People keep cancelling bookings as they are afraid of the virus," the official said.

Tours from Taiwan to mainland China have plummeted, with 90% of tour groups which had planned to go to China cancelling last month, the government said.