By Augustine Anthony

ISLAMABAD, Dec 18 (Reuters) - Pakistani authorities and World Health Organisation (WHO) experts were trying to determine on Tuesday whether bird flu had passed from human to human after the country reported its first human death from the virus.

Pakistani health officials confirmed at the weekend that eight people had tested positive for the H5N1 bird flu virus in North West Frontier Province since late October, of which one person, who worked on a poultry farm, died.

A brother of the dead person, who had not been tested, also died. It was not yet clear if he was a victim of bird flu.

One hundred people with symptoms of flu living in the vicinity had been checked but all tested negative, said a Ministry of Health spokesman.

"No linkage has been developed about human-to-human transmission. We are safe but we have to be very cautious," said the spokesman, Orya Maqbool Jan Abbasi.

The last human case was reported on Nov. 23, he said.

Health Secretary Khushnood Akhtar Lashari said on Monday some of the seven affected people had not worked with poultry and authorities were tracing who they had been in contact with.

Six had recovered while one was being treated, a provincial health official said.

Humans rarely contract H5N1, which is mainly an animal disease. But experts fear the strain could spark a global pandemic and kill millions of it mutates to a form that spreads more easily.

The area of the outbreak, near the towns of Mansehra and Abbottabad, about 60 km (40 miles) north of the capital, Islamabad, is in the foothills of the Himalayas.

Partly forested slopes are dotted with villages and small chicken farms.

A three-member WHO team, joined by officials from the Pakistan National Institute of Health, travelled on Monday to Peshawar, the province's capital where the patients were treated.

They were due to travel to Mansehra on Tuesday and were also expected to visit Abbottabad, where authorities reported the last H5N1 virus case in wild birds on Nov. 30.

The team would carry out epidemiological tests, Abbasi said.

Bird flu first appeared in Pakistan in early 2006, and several outbreaks of H5N1 were reported this year.

The Pakistani cases bring to nearly 350 the number of people worldwide who are known to have contracted the H5N1 virus, which has killed more than 200 people since 2003. (Editing by Robert Birsel and Sanjeev Miglani)

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