Margram, India, January 16, 2008Indian health workers in West Bengal state dispose of sacks of slaughtered chickenspart of a desperate attempt to curb the spread of a bird flu outbreak.

The deadly disease was spotted in the densely populated region on January 15, prompting officials to begin the weeklong program of slaughtering up to 400,000 chickens. Buddhadeb Bhattacharjee, West Bengal's chief minister, described the spread of the virus as "alarming," according to wire reports.

The outbreak coincides with the latest World Health Organization report on bird flu, released on January 16. The comprehensive update to a 2005 study found that at least a quarter of human cases involved no clear cause, suggesting that the disease can spread even to humans who are not in direct contact with infected birds.

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