(AFP)
Updated: 2005-12-22 16:54

Indonesia's bird flu death toll has risen to 11, amid worrying new evidence that the virus may be developing resistance to Tamiflu, the only drug known to be effective against it.

Test results from a World Health Organisation-affiliated laboratory in Hong Kong showed that a 39-year-old Indonesian man and an eight-year-old boy were the country's latest victims of the H5N1 strain of the virus.

"It's been confirmed. We were informed of the results this morning," Ilham Patu, a spokesman for Sulianti Saroso hospital, Indonesia's main centre for the treatment of bird flu, told AFP.

Indonesia, the world's fourth most populous nation, routinely sends samples of cases that test positive locally to Hong Kong for verification.

The man, a resident of South Jakarta, died on December 13, a day after being admitted to the hospital, while the boy died two days later at a private hospital in Jakarta.

Most victims have come from densely-populated Jakarta, where many people still live in close proximity to poultry, providing ideal conditions for the virus to pass to humans.

Hundreds of officials and veterinary students began visiting houses across the capital Thursday, looking for sick poultry as part of a nationwide campaign to fight the disease, agriculture ministry official Makmur told AFP.

"The surveillance is aimed at monitoring poultry that may be infected with bird flu," he said, adding that the students were trained last month by experts from the UN Food and Agriculture Organisation.

Meanwhile in Vietnam, bird flu had become resistant to the anti-viral drug Tamiflu in two fatal cases, a doctor said in what he described as a worrying development.

Tamiflu is considered a frontline defence against bird flu and the most effective treatment available to counter the H5N1 strain.

Menno de Jong, from the Institute of Tropical Diseases in southern Vietnam's Ho Chi Minh City, said Tamiflu was ineffective in fighting the virus in two girls who died despite being given full doses of the drug.

"Our two patients became resistant despite a full dose of treatment. Both died and in one patient there are some suggestions that the therapeutic failure and ultimately her death may have been caused by the development of resistance," he told AFP.

This patient was a 13-year-old, who died eight days after showing the first symptoms. The other, 18, died three weeks after the onset of symptoms.

"What will be important is to try to learn as much as possible from the next patients. We need to improve treatment of bird flu in this region," he said.

Vietnam has been the country hardest hit by bird flu, which has killed more than 70 people across Asia.

Meanwhile in China, state media reported that human trials of a bird flu vaccine had begun this week, with six volunteers being given shots.

The experiments, which will be carried out on 120 volunteers in Beijing, will last nine months, but preliminary conclusions are expected in around three months.

Various companies around the world are trying to develop a vaccine against the virus but the WHO's top official in China has said that they might be useless in the event of a pandemic, as the virus would have mutated.

Scientists fear that H5N1 may mutate into a form that could be easily passed between humans, sparking a pandemic with a potential global death toll of millions.