Only a month after authorities declared bird flu was under control in eastern India, veterinary workers began culling thousands of chickens on Monday to contain a fresh outbreak in poultry, Reuters reported. The outbreak was reported from West Bengal's Murshidabad district where 900 chickens and ducks died over the last two weeks, officials said. In January, the H5N1 virus had hit 13 of the state's 19 districts, including Murshidabad, bringing down poultry sales by more than 70 percent in the state, but it had a limited impact in rest of the country. Authorities had then culled more than 3.4 million birds in the state after the World Health Organization (WHO) described the outbreak as the worst-ever in India. There were no reported human cases of the bird flu. Experts fear the H5N1 strain could one day mutate into a form easily transmitted from person to person, leading to a pandemic that could kill millions worldwide. Officials in eastern India say bird flu among poultry could spread to new areas.