BEIJING (Reuters) - A Chinese man who died of bird flu lastmonth likely passed the disease on to his father, but there isno evidence the virus mutated into a form which can be easilypassed between humans, an official said on Thursday.

The man in the eastern province of Jiangsu was diagnosedwith the H5N1 strain of bird flu days after his 24-year-old sondied from the disease.

This rare case of two family members struck by the diseasedrew concern from health authorities, because humans almostalways contract H5N1 from infected birds.

Experts fear the virus could mutate into a strain thatjumps easily from person to person, risking wider outbreaks.

Chinese Health Ministry spokesman Mao Qun'an said it waslikely the man had caught bird flu from his son.

"The initial judgment is that it was an infection fromclose contact," Mao told a news conference, carried live ongovernment Web site www.china.com.cn.

"It has no biological features for human-to-humantransmission," said Mao, adding the father had now recovered.

Mao had already said in December that samples had indicatedno mutation of the virus.

But the ministry still did not know the cause of theinitial infection, as neither had had any contact with sick ordead birds, he said.

The virus does have a limited capacity for human-to-humantransmission, and other cases have been reported in Asia.

With the world's biggest poultry population and millions ofbackyard birds, China is at the centre of the fight againstbird flu. There have been other cases of human infectionwithout confirmed outbreaks among birds in the same area.

The latest cases brought the number of confirmed humaninfections of bird flu in China to 27, with 17 deaths.

(Reporting by Ben Blanchard; Editing by Nick Macfie)