BEIJING, Dec. 24 (Xinhuanet) -- Limited human-to-human bird flu transmission may have occurred in Pakistan, but there appeared to be no threat of further spread, a top WHO official said on Sunday.

    An initial testing on the samples of nine patients in areas north of Islamabad showed positive, and several of them are family members, indicating the possibility that the disease may spread human-to-human. They were the first reported human cases in Pakistan.

    Five brothers were sickened last month in the small city of Abbotabad, about 30 miles north of Islamabad. One was a veterinarian who was involved in slaughtering sick poultry infected with bird flu. Two of his brothers fell ill and died.

    A WHO team has sent the specimens to one of its collaborating laboratories for confirmation and was expected to be back in Geneva to piece together how the virus may have spread.

    "I think the team right now feels on initial analysis that this might be a small chain of human-to-human, non-sustained transmission," said Dr. David Heymann, the WHO's top flu official in Geneva.

    There have been no new infections reported for two weeks since Dec. 6, said the official, stressing there was no cause for alarm.

    On Dec. 22, six members of an extended family were tested negative of avian influenza, ruling out concern of possible bird flu cluster in Indonesia.

    The virus is supposed to spread to people primarily through contact with diseased poultry or birds.

    There have been 340 reported cases since 2003 when the virus re-emerged, of which 209 people have died, according to statistics released by WHO.

    (Agencies)