Asia's battle against the bird flu virus intensified as China halted poultry exports from three more regions with suspected outbreaks and Vietnam imposed a ban on all transport of chickens.

Complicating matters for China, the Ministry of Health also reported Saturday the winter's fourth confirmed case of Severe Acute Respiratory Syndrome, which killed nearly 800 people worldwide last year.

The patient, a 40-year-old doctor, had already been discharged from hospital in the southern province of Guangdong, the supposed origin of last year's outbreak, the ministry said on its website.

The World Health Organization had earlier urged China to learn from last year's SARS outbreak by swiftly containing the spread of bird flu, after authorities confirmed two more areas were affected and announced four new suspected outbreaks, making a total of seven hot spots.

"We have repeatedly said there is a brief window of opportunity to act within China," said Dr Julie Hall, a Beijing-based WHO infectious disease expert.

"This latest news strongly suggests that the window is getting smaller with each passing day," she said in a statement.

As part of efforts to contain bird flu in China, a chicken export ban has been widened to include the three new regions with reported outbreaks including its most populous city, the eastern metropolis of Shanghai.

Poultry is also being culled in the new suspected areas and poultry workers are being quarantined, officials told AFP.

"In six to seven hours, we've killed 35,000 chickens," said Yang Ping, an official in Anhui province where dozens of chickens died at a farm this week.

In response to the growing crisis, Hong Kong announced it had suspended the import of all live birds and poultry meat from the whole of mainland China.

WHO spokeswoman Maria Cheng said a similar strain was found in samples that were rechecked by a WHO-affiliated laboratory recently.

"One of our collaborating centers received two weeks ago a sample from a country that we are not naming that had been taken last April," she told AFP, adding that the virus looked to be a similar strain as H5N1.

Asia's first recent bird flu outbreak was reported in South Korea on December 15.

More than 28 million birds have now been culled across Asia to curb the disease which has killed 10 people in Vietnam and Thailand and been detected in chickens in eight other countries.

Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand and Vietnam have all reported outbreaks of H5N1 -- the deadliest strain of the virus -- among poultry, while Taiwan and Pakistan have reported weaker strains.

In Vietnam, where dozens of people are hospitalized with suspected infections of the virus which has hit two thirds of its 64 provinces, Prime Minister Phan Van Khai imposed a ban on all transport of chicken.

State media said Khai urged authorities to set up control stations and prevent the transport of poultry from one locality to another.

In Thailand, where Prime Minister Thaksin Shinawatra's administration is fending off accusations of a bird flu cover-up, a report said that a government agency believed the virus had reached the kingdom in November but suppressed the news for fear of damaging the economy and causing panic.

"The mass chicken deaths in Nakhon Sawan (province) and the bird-flu-like symptoms made us believe avian flu was already here at that time," National Institute of Animal Health director Nimit Traiwanatham said according to the Bangkok Post.

Thaksin said 14 million chickens have now been culled throughout the country, where the virus has spread to 32 of its 76 provinces including Phang Nga near the resort island of Phuket.

Seeking to reassure a public gripped by bird flu fears, he promised to pay three million baht (76,000 dollars) to the family of anyone who died from eating cooked chicken or eggs.

The United Nations' Food and Agriculture Organization (FAO) has warned that the mass cullings it considers absolutely necessary to contain the bird flu virus are not happening fast enough in poorer Asian countries.

But Indonesia appeared to backtrack Friday on a planned mass cull of chickens, with officials saying they would only carry out a selective slaughter despite pressure to join other affected nations in culling flocks.

The FAO said that world experts on bird flu, including specialists from the WHO and the World Organization for Animal Health, will meet in Rome next week to plot a strategy for controlling the disease.

(China Daily February 1, 2004)