The World Health Organization says the risk of a new SARS crisis hitting China is very small, considering the country's efforts to step up surveillance against the disease.

China has so far isolated more than 600 people in its capital of Beijing after a laboratory error led last week to the year's first SARS-related death.

The WHO has warned Chinese health authorities that next week's Labor Day holiday could exacerbate a spread of the latest outbreak as millions of Chinese criss-cross the nation by train, bus and plane.

Vice Minister of Health Zhu Qinsheng said anti-SARS measures had been stepped up ahead of the week-long break.

All the cases diagnosed in the most recent outbreak were traced to people who worked in a SARS laboratory in Beijing.

Last year's SARS epidemic killed nearly 800 people worldwide.