Indian officials are struggling to contain a serious outbreak of bird flu that has spread across nearly half of the eastern state of West Bengal.

India's Farm Minister, Sharad Pawar, said Wednesday the virus has been detected in nine of the state's 19 districts. Neighboring states are being asked to send medical staff to help deal with the outbreak.

West Bengal officials have set a new target of slaughtering 300,000 chickens a day and increased the number of veterinary teams to 600.

Bird flu was first detected in the Birbhum District of West Bengal last week. Since then, more than 400,000 birds have been killed.

Health workers are fighting an uphill battle in the state, with many local villagers unaware of the bird flu and refusing to give up their poultry to be killed.

Health officials continue to travel door to door to raise awareness and take blood samples from villagers to test for the virus.

The neighboring state of Bihar has also ordered the slaughter of poultry, as a precautionary measure.

Both Sri Lanka and Nepal have banned poultry imports from India.

The World Health Organization calls India's outbreak serious. According to the WHO, bird flu has killed at least 218 people worldwide since 2003, mostly in Asia. But there have been no cases of human infection in India.