An Indonesian poultry worker has tested positive for bird flu, in the country's first human case of the disease that has so far killed 54 people in Southeast Asia, health officials said Thursday.

The worker on the island of Sulawesi (search) is showing no symptoms of the disease, but blood tests show he was exposed to the H5N1 strain of the disease and has produced antibodies to it, said Hariadi Wibisono (search), director for the eradication of diseases transmitted by animals at the health ministry.

"This is the first case found," Dr. Georg Petersen, WHO's representative in Indonesia (search), told The Associated Press.

The bird virus has swept through poultry populations in large swaths of East and Southeast Asia. Tens of millions of chickens have either died or been slaughtered, while 38 people have died in Vietnam, 12 in Thailand and four from Cambodia since late 2003.

The Indonesian case is an ominous development in the global battle to prevent the bird flu strain from mutating into a form that passes easily between people and spawn a pandemic. Health experts have warned that Indonesia — which allocates only a tiny percentage of its gross domestic product to the health sector — may struggle to contain a major outbreak.

Indonesia has reported scores of outbreaks of bird flu at poultry farms across the country.

The infected worker was one of several dozen people whose blood was tested for the virus in a laboratory in Hong Kong as part of a routine surveillance program, said Wibisono. He said there was no need to keep the worker in hospital, or monitor his health.

"We have to raise our guard once again," Wibisono told The AP. "There is a possibility we will find more cases, but we hope that this does not transpire."

Last month, a government scientist identified the H5N1 strain (search) of bird flu in pigs on the nearby densely populated island of Java, raising fears that the virus could more easily spread to humans.

Experts worry that pigs infected with both bird flu and its human equivalent could act as a "mixing bowl," resulting in a dangerous, mutant virus that might spread to people more easily — and then from person to person.