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 cluster."

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.

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 cluster."

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.

"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.