BANGKOK, Sept 28 (AFP) - Experts said Tuesday that a suspected case of bird flu spreading between people in Thailand raised fears of a global health crisis and demanded Asian nations put more effort into tackling it.
Officials said their greatest fear was that the virus, currently a low-scale killer, could mutate into a contagious and lethal form that would threaten millions of human lives.
They said that the longer bird flu remained endemic in Asia, after nearly a year of outbreaks among humans and birds across the region, the greater the threat of a deadly human form emerging.
Tests have not shown that the lethal H5N1 virus has mutated, but the death of a Thai woman, who is believed to have caught bird flu from her sick daughter, has sent shivers through the medical community.
Pranee Krongkaew, 26, died eight days ago after caring for her fatally ill 11-year-old daughter in hospital to become the 29th confirmed victim of the bird flu in Asia this year.
Officials have taken some comfort that the woman only appeared to have contracted bird flu after a prolonged period of contact with her daughter, who also died of suspected bird flu, and was apparently restricted to one family.
"If the virus does mutate it could become a pandemic strain and that is the base line worry we have for any influenza virus," Thai health ministry vaccine expert Supamit Chunsuttiwat told AFP.
Tests were continuing in Thailand and the US to determine if there had been any variations in the virus that killed the Pranee.
"We agree that it's a probable human-to-human case," World Health Organisation (WHO) spokesman Dick Thompson told AFP. "It raises our concern, that's for sure, but it's not unexpected."
The lethal H5N1 strain of bird flu has predominantly been transmitted to humans in the Asian outbreak from poultry, most likely through airborne faeces that carry the bug.
The big concern for health officials is that H5N1 would mingle with the ordinary flu virus, such as in someone who is suffering from it, or with an animal such as the pig that can harbour both forms.
That way, a mass killer could emerge: a virus that is both lethal and contagious.
Most viruses do not mutate that much, but influenza, like the human immunodeficiency virus (HIV), is a notorious exception.
A mutated bird flu virus erupted among humans in 1918, killing as many as 40 million people, and lesser pandemics occurred in 1957 and 1968.
The UN's Food and Agriculture Organisation (FAO) said it could only make a full assessment of the current threat once all test results were in.
"FAO is eager to see further evidence and information in order to help us to understand better what might have changed in the biology or genetic make-up... to give rise to this probable human-to-human transmission," FAO regional head He Changchui told reporters in Bangkok.
He also warned that the virus was still out of control in Asia, making efforts to prevent human-to-human transmission harder.
"It will probably not be eradicated in the near future... today's announcement reinforces the need to control and eradicate (bird flu) from animals," he said.
He outlined a list of urgently needed improvements including public awareness and preventive measures.
Tuesday's announcement raised the possibility that other deaths in the region from bird flu had been caused by human-to-human transmission.
Two sisters died of bird flu in northern Vietnam in January, having contracted the virus along with their brother and his wife.
But Thai officials played down the threat. "This isolated episode of probable human-to-human transmission would not pose a significant public health threat," the health ministry said in a statement.