HANOI, Jan 3 (Reuters) - Bird flu has killed 350 white-winged ducks in northern Vietnam this week, the first outbreak in poultry detected this year, the government said on Thursday.

The virus was found at a farm raising two-month-old ducks in Thai Nguyen province and animal health workers slaughtered all the remaining birds there to prevent it spreading, the Animal Health Department said in its daily report.

Last month, the H5N1 bird flu virus killed a four-year-old boy from an ethnic minority group in the northern province of Son La, Vietnam's first human case in nearly five months.

At the same time, the government also said the virus had hit hundreds of ducks and chickens in the Mekong Delta province of Tra Vinh in the south. The province is still on the government's bird flu watchlist, along with Thai Nguyen.

Officials said they did not find bird flu in or around the area where the boy who was killed last month, leading them to suspect wild birds might have spread the H5N1 virus.

The World Health Organization has confirmed the boy's death from bird flu, which has now killed 47 of the 101 people infected in Vietnam since late 2003.

Officials say cold weather now affecting northern provinces and a rising demand for poultry ahead of the Lunar New Year festival early next month could help revive and spread the H5N1 virus, which appears to thrive best at cool temperature.

Globally, the H5N1 virus has killed 212 people out of 343 known cases, with most of the deaths in Indonesia, Vietnam, Thailand and Egypt, the WHO figures show. (Reporting by Ho Binh Minh; Editing by Alex Richardson)

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