A family of eight infected with bird flu in Indonesia likely passed the
disease among themselves, but world health officials said Wednesday 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 person to person since the start of the outbreak in Hong
Kong in 2003, World Health Organization spokesman Gregory Hartl said.
But this case may mark the first time bird flu has passed from person to
person to person, a top US health official said.
The previous clusters all involved someone who was infected by a sick bird
and then spread the virus to others. This new cluster appears to involve a
cascade of transmission, said Dr. Julie Gerberding, director of the US Centers
for Disease Control and Prevention, in a telephone briefing from Geneva.
The family members' close physical proximity is probably responsible for the
spread of the disease, Hartl said.
"It fits the kind of pattern perfectly which we've seen so far," Hartl told
The Associated Press. Global and U.S. health officials say tests on virus
samples taken from the family do not indicate any significant changes.
Investigators say the family, living in the remote northern Sumatra village
of Kubu Sembelang, were infected with a strain of H5N1 bird flu that was
genetically the same as the virus found circulating in the area earlier. Tests
are still being carried out on poultry there.
Infections have not been detected in health-care workers or others in the
village, but those who may have come in contact with the family are being given
Tamiflu as a precaution, Gerberding said.
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.
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 the seven family members who caught bird flu have died, the most
recent on Monday. An eighth family member who died was buried before tests could
be done, but she was considered to be among those infected with bird flu.
"... 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.
In the three previous family clusters - in Indonesia, Thailand and
Vietnam - the number of infected relatives was much smaller, Hartl said.
CDC officials noted that the evidence for human transmission was stronger in the
Indonesia and Thailand clusters, but human transmission could not be ruled out
in the Vietnam cluster.
Health workers have found no sign the latest 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, Peter Cordingley, spokesman for WHO's Western Pacific
region.
Bird flu has killed 124 people worldwide since the virus started ravaging
poultry stocks across Asia in 2003.
