Bird flu likely is passing from human to human

GENEVA – A family of eight infected with bird flu in Indonesia likely passed the disease among themselves, but the World Health Organization said today there is no reason to raise its pandemic alert level.

It is the fourth — and largest — family cluster of bird flu cases likely transmitted from human to human since the start of the outbreak in Hong Kong in 2003, World Health Organization spokesman Gregory Hartl said.

The family members' close physical proximity is probably responsible for the spread of the disease, but that still does not indicate the virus is mutating into a form that could cause a pandemic, Hartl said.

"It fits the kind of pattern perfectly which we've seen so far," Hartl told The Associated Press. "It still says that the virus hasn't mutated."

WHO has suspected that in rare cases bird flu may have passed from one person to another, although people usually catch it from chickens and other poultry.

Experts have long believed the virus is spread when people breathe it in — possibly in dust from bird droppings or in droplets sneezed or coughed by humans into the air.

But it remains unclear exactly how the virus spreads in family groups — whether through respiratory systems, food, infected surfaces or a combination of these, Hartl said.

"Which transmission mode is most important, we really don't know yet," he said. "When you get all of these things together, it becomes perhaps more likely."

Other experts have suggested family members have a genetic weakness to the disease. In all four family clusters recorded so far, only direct blood relatives — not spouses — have caught bird flu.

Testing indicated there had been no significant mutations in the virus, WHO said. Experts have feared a mutation of the virus into a strain that could easily pass among humans could set off a flu pandemic, with the potential to kill millions worldwide.

WHO will leave its pandemic alert level unchanged at 3, where it has been for months, meaning there is "no or very limited human-to-human transmission."

Six of seven people in the extended family in northern Sumatra who caught bird flu have died, the most recent on Monday. An eighth family member who died was buried before tests could be conducted, but she was considered to be among those infected with the H5N1 strain of bird flu.

"When it spreads from human to human, if this is indeed the case here, and it's certainly something that we're looking at, it apparently can only spread between human to human when there is extensive and close contact between someone who is already showing clinical signs of the disease and the uninfected person," Hartl said.

Health experts are trying to determine if the virus has spread outside the family. "That would be very worrying. We haven't seen any signs of that yet," said Peter Cordingley, spokesman for WHO's Western Pacific region.

In the three previous family clusters — in Indonesia, Thailand and Vietnam — the number of infected relatives was much smaller, Hartl said.

Health workers have found no sign the Indonesian case has moved outside the family, and there is also "no evidence that efficient human-to-human transmission has occurred," WHO said in a statement.

Still the size of the cluster and the failure to determine the source of the infections was worrying, Cordingley said.

Bird flu has killed 124 people worldwide since the virus started ravaging poultry stocks across Asia in 2003.

AP correspondents Margie Mason in Hanoi, Vietnam, Anthony Deutsch in Jakarta, Indonesia, and Alexander G. Higgins in Geneva contributed to this report.