Noted Chinese contagious disease expert Zeng Guang called on Saturday for continued vigilance and effective anti-SARS efforts despite the decline or absence of new SARS cases in the past few days on China's mainland.

Zeng, an infectious disease expert with the Beijing-based National Centre for Disease Prevention and Control, warned that a lack of vigilance could result in a dangerous situation.

Zeng said the decline of SARS cases is the result of a series of rigorous measures taken by the Chinese Government. These measures include efforts to reduce infection rates in hospitals, a surveillance and quarantine system, strict isolation orders for SARS patients and for suspect cases, the close monitoring of the floating population and high public vigilance against SARS.

With the ebb of the SARS epidemic and the gradual return to normality, ill people are visiting hospitals again, students are returning to school, migrant workers are flocking back to the capital and entertainment venues are re-opening.

A renewed outbreak could therefore occur if the public were to lower its guard, and transmission were to occur from sources from home and abroad, Zeng warned.

In addition, mankind has yet to fully understand the SARS virus, its transmission mode, and the duration of its survival under normal circumstances.

Hence, "China should persist in its anti-SARS efforts and pay close attention to infections within hospitals," said Zeng.

"It is totally unnecessary to lower diagnosis standards of SARS in order to pursue a zero increase on new SARS case," Zeng said, referring to the criteria set by the World Health Organization to lift the travel advisory against SARS-affected places.

The WHO's conditions include: no more than 60 SARS patients in hospitals, below five new SARS cases per day for five straight days, all SARS patients in isolation and no exports of infections to outside areas.

The WHO's final requirement stipulates that only when the SARS- affected area reports no new cases for 20 consecutive days, can it consider lifting the travel advisory.