By Adhityani Arga

JAKARTA, Jan 30 (Reuters) - An outbreak of bird flu in poultry in India's West Bengal state is "coming under control", but authorities still need to break the chain of transmission of the H5N1 virus, the United Nations influenza coordinator said in an interview on Wednesday.

"I would say that it is coming under control," David Nabarro told Reuters, "And the final test of whether it's under control would be whether or not authorities are able to really dampen down the new outbreaks of H5N1 particularly in West Bengal."

Bird flu has spread to 13 of 19 districts in India's West Bengal in the fourth outbreak of the H5N1 strain since 2006, with samples of dead chickens testing positive in two new districts, officials said on Monday.

In neighbouring Bangladesh, the disease has spread to 29 of its 64 districts since March last year despite mass-culling of poultry.

"What the authorities need to try to avoid is the continous transmission of the H5N1 virus so you almost stop noticing the outbreaks," Nabarro said, sitting in his suite in a five-star hotel in the Indonesian capital Jakarta.

The public health expert is on a four-day visit in the Southeast Asian nation, where he meets ministers and experts to review Indonesia's efforts to stamp out disease.

Nabarro said a major problem is that most poultry in West Bengal and Bangladesh are raised in backyards and farmers have been reluctant to cull their birds in the fear of losing a vital source of income and nutrition.

"In both the Bangladesh and the West Bengal situation the key dilemma that government faces is on the one hand wanting to get the virus under control and to reduce infections," Nabarro said.

"On the other hand, to try not to increase poverty among already very poor rural communities."

"But I am really very pleased with the general approach that's been taken in both settings."

In West Bengal over 2 million birds have already been culled since the H5N1 virus hit the state earlier this month, and authorities are planning to ban rearing backyard poultry in infected districts for at least three months.

Nabarro praised Indonesia's progress in containing the spread of bird flu despite the recent spike in human cases with six deaths in January alone.

"If there had not been a strong response by the authorities, it is my belief that we would have much higher rates of human disease in this country."

"The levels of human infections are still mercifully quite low... but a lot more has to be done."

Experts fear the H5N1 strain could mutate into a form easily transmitted from person to person, leading to a pandemic that could kill millions.

There are no human infections have been reported in India and Bangladesh, while Indonesia leads the world's toll from the disease with 124 human cases of which 101 have been fatal.

(Editing by Sanjeev Miglani)

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