Health officials in Thailand say a woman who died from the bird flu virus last week may have caught it from her daughter. Twenty-nine people have died in Thailand and Vietnam since the outbreak was detected in January, but the previous victims appear to have caught the disease directly from birds.

Thai health officials Tuesday said they have no evidence that the woman who died last week came into contact with sick chickens. The woman lived near Bangkok but went to her home village to care for her daughter, who later died.

Doctors believe the daughter caught the H5N1 virus from chickens.

Thai health official say they need further study before they can confirm whether the mother caught the virus from her daughter or from the village environment.

If tests show the woman caught the disease from her daughter, it would be the first confirmed human-to-human transmission of the H5N1 virus. International health organizations worry about a pandemic if the virus changes so it can spread easily from human to human.

Thai Health Ministry spokeswoman Nitaya Chamruang Mahebhol says, however, that tests on the most recent victim show the virus had not changed genetically. "So far, the virus H5N1 has not mutated yet, as confirmed by the laboratory genetic sequencing," she said.

World Health Organization spokesman Peter Cordingley says that chances of a pandemic, while possible, remain remote. "If this is human-to-human - if it is - it seems to have been contained in a very small family unit," he said. "And if that is the case then quite clearly the virus still has not established the ability to jump from human to human."

Nevertheless, the Thai government has issued a nationwide health alert, which means greater scrutiny of patients complaining of pneumonia or flu-like symptoms.

Thai poultry growers, who have yet to recover from losses of millions of birds they had to cull due to the epidemic, have been told to report all suspicious deaths in their flocks.

The U.N. Food and Agriculture Organization warned in a statement Monday that bird flu is a global health crisis and will not be eradicated in the near term.