GENEVA (Reuters) - The eight individuals in Pakistan whoare suspected to have bird flu probably have a combination ofinfections from poultry and limited person-to-persontransmission from close contact, a top World HealthOrganization expert said on Tuesday. Keiji Fukuda, coordinatorof WHO's global influenza program, said while unconfirmed, anyhuman-to-human spread seemed similar to previous outbreaks inThailand and Indonesia -- affecting close family members caringfor sick loved ones.

There was no immediate cause for alarm and the UnitedNations agency was not raising its level of pandemic alert forthe time being, he said, adding it was very reassuring that "weare not seeing large increases in the number of cases."

"Right now it doesn't look like pure human to humantransmission. It looks like the veterinarian, who was the indexcase, and a number of other suspect cases had poultryexposure," Fukuda told Reuters in an interview.

"It is definitely possible that we have a mixed scenariowhere we have poultry to human infection and possible human tohuman transmission within a family, which is not yet verified."

But human to human transmission "would not be particularlysurprising or unprecedented," he added.

Eight people have tested positive for the H5N1 bird fluvirus in North West Frontier Province since late October, andone of the confirmed cases has died. A brother of the dead manalso died, but was never tested, so is not counted among them.

H5N1 is mainly an animal disease, but experts fear it couldmutate into a form that could spread easily between people,causing a pandemic which could kill millions of people. InThailand, a mother was killed by the virus in 2004 aftercradling her dying infected daughter all night. The largestknown cluster of human bird flu cases worldwide occurred in May2006 in Indonesia's North Sumatra province, where as many asseven people in an extended family died.

Three WHO experts, led by Hassan El-Bushra of its regionalCairo office, is in Pakistan helping to investigate theoutbreak.

The "index" case, who recovered, is a veterinarian whohelped with culling operations and it is his two brothers whodied after taking care of the ill man, according to Fukuda.

"This type of close contact we know can result in human tohuman transmission sometimes," he said.

"Right now, based on the information we have, theinvestigation going on and the feedback from the field team, wedon't have anything pointing to push the alarm bells orincrease the (pandemic alert) phase," he added.

The WHO uses a series of six phases of pandemic alert togauge the level of threat. The world is currently in phase 3, anew influenza virus subtype is causing disease in humans, butis not yet spreading efficiently or sustainable among humans.

"In terms of public health implications, we are looking forhuman to human transmission where casual contact can lead toinfections and allow big outbreaks in communities," Fukudasaid.

A team from the U.S. Naval Medical Research Unit NAMRU-3laboratory in Cairo was expected in Pakistan on Wednesday tocarry out further tests on the samples from the suspect cases.