In Hong Kong, fears are growing that Severe Acute Respiratory Syndrome is spreading from one housing complex to another. Around Asia, fear of the disease has pushed many governments to consider bans on visitors from infected areas.

Ten days after Hong Kong sealed off a residential complex where Severe Acute Respiratory Syndrome was spreading, at least 30 residents of a neighboring complex have fallen ill with the disease.

Almost 1,000 people in Hong Kong have been diagnosed with SARS. A quarter of them are residents from the Amoy Gardens high-rise apartment complex.

The government says many Amoy Gardens residents fled their homes after the outbreak, and went to live with family and friends in nearby buildings, spreading the disease.

But the government is not ruling out the possibility that cockroaches or tainted water carried the virus to neighboring buildings.

World Health Organization spokesman Peter Cordingley says many theories are being studied.

"The Hong Kong government has been doing environmental studies [on] piping, sewage, water, cockroaches, rats, the building site next door ... we have been doing more data study on the families and their connectivity," he said. "Without understanding Amoy Gardens we can not expect the problem in Hong Kong to be contained."

SARS has hit more than 2,600 people in at least 15 countries, and killed more than 100. The WHO is particularly concerned about Hong Kong, as the outbreak shows no signs of slowing. The U.N. agency warned travelers to avoid visiting the city after it became clear outbreaks around the world were tied to people who had been in Hong Kong.

Mainland China, which reports more than 1,200 SARS cases and more than 50 deaths, is also seen as a health threat to neighboring countries.

Malaysia says it will stop issuing visitor visas to Chinese nationals, to prevent the spread of SARS.

The Philippines also is telling its citizens to avoid travel to Hong Kong. The government is considering a one-month ban on visitors from Hong Kong. More than 100,000 Philippine citizens work in Hong Kong, and many travel home for holidays such as Easter, which is next week.

SARS sufferers display flu-like symptoms, which can quickly develop into a serious and potentially deadly form of pneumonia.