KOLKATA, India (AFP) - India's bird-flu hit state of West Bengal appealed to New Delhi to allow the United States and China to come to its aid in battling the disease, an official said on Wednesday.

The deadly H5N1 strain of bird flu has now been found in 13 of 19 districts in the eastern Indian state of 80 million people since the outbreak began two weeks ago and bird deaths in new areas have been reported in the last day.

"We need foreign help to stem the deadly virus, which is spreading at an alarming rate," said West Bengal animal resources minister Anisur Rahaman, who has also expressed fears the disease could soon show up in humans.

"I have urged the chief minister to have talks with the federal government so that we can approach the United States and China for help."

Both countries have already offered to assist the state, local reports have said.

"We have an experience that bird flu spreads very quickly so it needs to be tackled fast," said United States Ambassador to India David C. Mulford, according to a report in the Indian Express Tuesday.

"It has to be nipped in the bud before it moves forward."

It is India's third outbreak of bird flu, but by far its most serious.

The United States has offered technical help to the surveillance teams as well as protection gear and other equipment, the Express report said.

State minister Rahaman said widespread culling -- some two million chickens have been slaughtered so far out of a target of three million -- had not yet stopped the disease spreading.

"Nearly 3,000 poultry died Tuesday in an organised poultry farm" in a district bordering neighbouring Bangladesh, said Rahaman.

"Samples of dead poultry have been sent for testing."

House-to-house surveillance is underway in that district as well as two others close to state capital Kolkata, home to 13.5 million people.

Authorities are trying to prevent the virus reaching Kolkata by using checkpoints to stop the smuggling of infected birds.

Humans typically catch bird flu by coming into direct contact with infected poultry, but experts fear the H5N1 strain may mutate into a form easily transmissible between people.

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