BANGKOK, Jan 24 (Reuters) - The H5N1 bird flu virus has re-emerged in a northern Thai province for the first time since March last year, forcing the slaughter of 10,000 chickens, an Agriculture Ministry official said on Thursday.

The outbreak occurred on a farm in Nakhon Sawan, 240 km (149 miles) north of Bangkok, where the owner reported 4,085 chickens had died earlier this month, senior Livestock Department official Nirundorn Aungtragoolsuk told Reuters.

"The H5N1 virus was found on the farm and we have culled the rest of them," he said of the birds slaughtered in one of four closed chicken houses on the farm.

The others house 45,000 chickens which had shown no signs of the deadly avian influenza virus, he said.

The virus last reappeared in northern Thailand in March 2007, but there have been no new reports of human infections in the country, where the virus has killed 17 people since 2003.

Of the 351 human cases recorded since H5N1 re-emerged in Asia in 2003 and spread to parts of Africa and the Middle East, 219 have died, according to the World Health Organization (WHO).

The virus does not currently spread easily between humans, but scientists fear it could mutate into a form that would trigger a global pandemic, killing millions of people. (Reporting by Panarat Thepgumpanat; Writing by Orathai Sriring; Editing by Darren Schuettler)

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