By Bappa Majumdar

KOLKATA, India, Feb 5 (Reuters) - India's worst outbreak of bird flu appears to be under control, with a massive cull of poultry to contain the disease almost completed, health officials said on Tuesday.

More than 3.4 million birds have been culled in West Bengal, where 13 of the 19 districts have been affected by the H5N1 bird flu virus since the disease was first reported last month, state officials said.

"Culling is almost over and we are now conducting mopping up operations in the infected areas," Anisur Rahaman, the state's animal resources minister, told Reuters.

Disinfecting villages affected by avian influenza could continue for several weeks, he said.

"But the overall situation is totally under control," Rahaman added.

India said tests of at least 23 people, including several veterinary staff, who were held in isolation wards with symptoms of influenza had turned out negative for H5N1.

"But we are still keeping a close watch," Sanchita Bakshi, the director of health services in West Bengal, said.

India has not reported any human infections of the H5N1 bird flu virus in its four outbreaks of avian influenza since 2006.

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

About 60 percent of India's 1 billion plus people live in rural areas close to livestock, just like in many other parts of Asia, raising the risks of the bird flu virus infecting people.

In West Bengal's state capital, Kolkata, one of the biggest cities in India, authorities encouraged people to eat chicken to help the poultry industry as many people opted for fish and mutton dishes following the outbreak.

Egg exports from the world's second largest producer have also dropped about 50 percent, leaving the industry with losses of around $20 million, trade officials said.

India said culling would also take place in states bordering West Bengal and a special watch was in place in districts bordering Bangladesh.

Authorities said the virus could have originated from Bangladesh, where officials were struggling to contain a massive outbreak of bird flu.

"We are keeping a watch on our borders with Bangladesh and other states as the idea is to minimise the chances of bird flu spreading," Rahaman said.

Many unwilling villagers resisted the authorities efforts, letting most of their backyard poultry free when culling teams arrived. There were reports that some chickens and ducks were smuggled out at night from infected districts. (Editing by Alistair Scrutton and Alex Richardson)

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