Thailand confirmed its third death from bird flu, a 58-year-old Thai woman who died last week, although 10 others are believed to have died of the virus.

An 18-year-old boy in Vietnam became the country’s eighth confirmed fatality.

The World Health Organisation (WHO) is now examining the possibility that a Vietnamese man contracted the virus from his two sisters.

If so, it would prove that the virus can pass from human-to-human threatening an escalation in the spread of the disease.

Millions of chickens in South-East Asia have been slaughtered to prevent the spread of the disease which passes from animal to human through close contact with infected live poultry.

The WHO has warned that the highly pathogenic H5N1 strain present in eight Asian nations could kill millions across the globe if it combines with a human influenza virus to create a new virus transmissible among humans.

Thaksin Shinawatra, the Thai Prime Minister, criticised the WHO for making its fears public, saying researchers should only reveal their theories if there was a good prospect of them being confirmed.

If the possibility is higher than 5 per cent they should say something, but if it is under 5 per cent they should not say anything. The possibility of human-to-human transmission is 0.00001 percent," he said.

Six countries hit by bird flu, Cambodia, China, Indonesia, Japan, Laos and South Korea, have not reported any human infections.

China announced five new suspected cases in poultry on Monday, including one in its remote northwestern region of Xinjiang - underlining the potentially broad range of the disease.

Xinjiang is more than 1,000 miles from the southern region of Guangxi, where China’s first case of bird flu was confirmed last week.

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