Beijing, Jan. 31 (Reuters): China’s window of opportunity to stop the spread of bird flu is narrowing, the WHO said, while the country stepped up checks on poultry nationwide for signs of the deadly virus.

That window closed a bit more today, when China announced two new areas suspected of having cases of bird flu — one in the central province of Hubei and one in the southern province of Guangdong.

China confirmed outbreaks in the provinces of Hubei and Hunan to be the lethal H5N1 strain of avian influenza yesterday, and announced four new areas of suspected infection — two in Anhui province, one in Guangdong and one in the city of Shanghai.

“We have repeatedly said there is a brief window of opportunity to act within China. This latest news strongly suggests that the window is getting smaller with each passing day,” said WHO disease surveillance specialist Julie Hall.

Earlier this week, China confirmed an outbreak in the southern region of Guangxi bordering Vietnam. Bird flu has spread rapidly to 10 Asian countries, killing at least eight people in Thailand and Vietnam. Chinese authorities have been culling poultry within 3 km of infected farms, vaccinating birds within 5 km and established national command headquarters.

Today China also halted exports from Anhui, Guangdong and Shanghai, following bans on shipments abroad from the other infected areas. On the outskirts of China’s financial hub, Shanghai, teams of inspectors descended on villages and markets without warning yesterday, residents said, seizing tens of thousands of fowl, spraying disinfectant and burning piles of bird dung. At least 20,000 chickens had been culled in a single day at Shanghai's largest wholesale poultry trading station in an outlying northeastern district.