Hong Kong has followed Singapore's example in invoking an old quarantine law not used in decades. The measure is aimed at stemming the spread of Severe Acute Respiratory Syndrome, an illness that has sickened about 1,400 people worldwide.

Hong Kong Chief Executive Tung Chee-hwa imposed a quarantine on those exposed to the disease and closed the city's schools. He says the measures are aimed at "intercepting the spread" of Severe Acute Respiratory Syndrome, known as SARS.

Hong Kong is one of the cities worst hit by the disease. The number of people with SARS has soared to more than 300, less than a month after the first case was found in the city. Across the border, in mainland China, more than 800 cases have been identified. Southern China now accounts for the majority of the world's SARS cases.

Under Hong Kong's quarantine laws, people showing symptoms will be hospitalized and isolated. Those who have had contact with infected persons must report for a daily checkup.

Health Secretary Yeoh Eng-Kiong calls the measures "draconian", but necessary. "We are trying to encourage people to come to our designated medical centers to report every day, but if they do not follow the instructions, we have the power to fine them, remove them to a place of quarantine, or they can be imprisoned up to six months," he said.

More than 1,000 people will be immediately quarantined. Singapore has closed schools and quarantined more than 800 people exposed to SARS.

Victims of the disease suffer severe flu-like symptoms that often progress to a severe form of pneumonia. The disease first appeared in southern China late last year. Worldwide, nearly 1,400 have been infected and more than 50 have died.

Researchers in Hong Kong have announced findings supporting theories that a virus similar to the one that causes the common cold is behind SARS.

The teams also say they have created a diagnostic test to identify cases.

The World Health Organization is warning travelers in Asia to be alert for flu-like symptoms. That warning and media coverage about the disease is discouraging tourists from visiting Hong Kong, Singapore, southern China, and Vietnam, where dozens of cases also have been found.

In Hong Kong, The Rolling Stones rock group postponed concerts scheduled for Friday and Saturday because of the outbreak.

But the Rugby Sevens, Hong Kong's premier sporting event that draws thousands of visitors each year, will begin Friday as planned.