Race to find mystery fatal bird flu source

WASHINGTON - United States health experts are trying to trace anyone who had contact with an Indonesian family who died of bird flu amid fears they may have infected each other.

The seven deaths in the family in Kubu Sembilang village, north Sumatra, over the past few weeks is the largest family cluster of bird flu victims known.

Villagers were co-operating with health investigators and there was no sign that the H5N1 avian flu virus had infected anyone outside the family, said US Centres for Disease Control director Dr Julie Gerberding.

Nonetheless, financial markets were jittery and buyers drove up stocks in companies working on influenza vaccines and drugs in what one analyst called a "knee-jerk reaction".

World Health Organisation and Indonesian health officials cannot find the source of the infection in Sumatra, but Gerberding said genetic sequencing showed the H5N1 virus had not mutated substantially.

"The concern that has been raised ... is the potential for evidence for human-to-human transmission.

"This is the leading hypothesis that is under investigation. The likely source was poultry exposure, as we have seen time and time again."

But the case may represent what is known as tertiary transmission - someone may have been infected by a chicken and infected a relative, who in turn infected someone else.

While cases of human-to-human transmission have been seen before - in Thailand and Vietnam - doctors believe that one person only infected one other in those instances and the chain of transmission stopped there.

"A person-to-person-to-person transmission chain is very important ... that is why there has been such attention and such an effort," said Dr Gerberding.

Dr Firdosi Mehta, acting WHO representative of in Indonesia, said experts in Kubu Sembilang were acting to contain any further spread.

"We are going wide, contacting the various contacts, putting whoever has had close contact on [anti-viral] Tamiflu, basically putting family who have not been affected on Tamiflu as a precaution," Dr Mehta said.

"There is active surveillance in the village and fever surveillance to look for any more cases that are occurring outside this immediate family cluster."

Bird flu has infected 218 people in 10 countries and has killed 124 since it re-emerged in Asia in 2003.

It mostly infects birds, but if it changes into a form that easily passes from person to person it could touch off a deadly pandemic.

- REUTERS