June 23, 2006

H5N1 mutated in Indonesia, stayed in cluster: WHO

By Stephanie Nebehay and Fitri Wulandari

GENEVA/JAKARTA (Reuters) - The H5N1 bird flu virus mutated
somewhat among Indonesians in the largest known human cluster,
but did not evolve into a more transmissible form, the World
Health Organization (WHO) said on Friday.

A spokeswoman for the U.N. agency, Maria Cheng, said the
result came from its investigation into a cluster of cases in
northern Sumatra, where the virus killed seven members of a
single family in May.

"There was a mutation found," she told Reuters in Geneva,
in response to a query. "But it did not mutate into a form that
is more transmissible because it didn't seem to go beyond the

Malik Peiris, a leading H5N1 expert from Hong Kong, told
reporters on the sidelines of a bird flu experts' meeting in
Jakarta that it was common for the influenza virus to mutate.

"Influenza viruses always mutate. That's of course the
reason why people are concerned that as we go on longer and
longer the virus may change to become more transmissible. But
that does not happen so far."

The mutated virus was detected in samples taken from the
last two victims in the cluster -- a son who transmitted it to
his father -- providing the clearest proof yet of human to
human transmission, Cheng said.

"In the past we haven't had such definitive laboratory
evidence to prove human to human transmission but in this case
we do."

But three weeks later, the man's wife has not shown any
signs of the disease, she added.

"We did not detect any transmission so it was a dead-end
chain of transmission," Cheng added.

Indonesian and WHO officials closely monitored more than 50
contacts of the victims in the northern Sumatra case, keeping
them in voluntary home quarantine following the outbreak, but
none developed symptoms, according to the Geneva-based agency.

The H5N1 strain of avian influenza has spread rapidly from
eastern Asia in recent months. It almost exclusively infects
birds but has killed 130 people since 2003, mostly in Asia.

Experts believe it poses the greatest threat yet of a
pandemic, a global epidemic of flu that could kill millions, if
it becomes able to pass easily from human to human.


Keiji Fukuda, the WHO global influenza program coordinator,
told a news conference ending the three-day experts' meeting in
Indonesia that what the WHO had been looking at in the cluster
case was whether to move to a pandemic alert.

"The answer is clearly no. We see no evidence of the start
of pandemic influenza," he said.

The experts at the conference said that while Indonesia was
making a substantial effort to combat the H5N1 bird flu virus,
the situation was not yet satisfactory.

"Highly pathogenic H5N1 avian influenza is widespread and
well established in Indonesia but the full extent is unknown.
It is believed that large numbers of animal infections are
undetected," a joint statement by the experts said.

"The public is still lacking basic knowledge of the risks
to their poultry and themselves and therefore their
understanding of control methods in poultry and how to protect
themselves is minimal."

Indonesia has seen a steady rise in bird flu human
infection and deaths. The virus has infected 51 Indonesians and
killed 39 of them and is endemic in poultry in nearly all the
country's 33 provinces.