The danger of the virulent H5N1 strain of the disease was illustrated in Indonesia, where a man from the outskirts of Jakarta died of bird flu Thursday, bringing the country's death toll to 98.

On Wednesday, Vietnam announced its first death this year, taking its toll to 48 since the virus began devastating Asian poultry stocks in late 2003.

Also Thursday, Thailand reported its first outbreak in 10 months.

Bird flu has killed at least 221 people worldwide, according to the World Health Organization. Although it remains hard for humans to catch, experts fear it will mutate into a new form that spreads easily among people, potentially sparking a pandemic.

Fears of the virus spreading in the chaotic crowded streets of Calcutta prompted city health officials to send teams to inspect city markets for signs of the disease after it was discovered just 30 kilometres from the city of 14 million people.

Health authorities - hampered by crippling bureaucracy, a shortage of qualified personnel, ignorance among villagers and even bad weather - have struggled to contain the outbreak, a stark reminder that much of the country has been left behind as India emerges as a global economic power.

'Culling is slow and ham-handed,' said West Bengal Poultry Welfare Association President Sheikh Nazrul Islam, who said losses to the poultry industry totaled 1 billion rupees (S$36.4 million) in the last week.

While India has successfully contained two previous outbreaks, both were in large poultry farms.

About 700,000 birds have been slaughtered since the disease was discovered last week in the state, and health workers plan to kill another 1.4 million, said state Animal Husbandry Minister Anisur Rahman.

'We are doing our best to stop the virus from spreading to Calcutta and other districts,' Rahman said, adding that some 750 teams were involved in the slaughter.

Also Thursday, the UN Food and Agriculture Organization issued a statement in Rome warning that despite international efforts bird flu remains a global threat.

'The H5N1 avian influenza crisis is far from over and remains particularly worrying in Indonesia, Bangladesh and Egypt, where the virus has become deeply entrenched despite major control efforts,' FAO Chief Veterinary Officer Joseph Domenech said in the statement.

'The virus has not become more contagious to humans but has managed to persist in parts of Asia, Africa and probably Europe. It could still trigger a human influenza pandemic,' he said. -- AP