JAKARTA (Reuters) - Limited human-to-human transmission of bird flu might have occurred in an Indonesian family and health experts are tracing anyone who might have had contact with them and putting them on antiviral drugs as a precaution, the World Health Organization said.
But a senior WHO official said in Jakarta this was not the first time the world was seeing a family cluster and stressed that fresh scientific evidence has shown the virus in Indonesia has not mutated to one that can spread easily among people.
Still, financial markets were spooked by the first statements out of the WHO. Commodity prices in the U.S. came under pressure while European markets slipped as investors turned jittery.
Concern has been growing about the case in north Sumatra in which seven family members from Kubu Sembilang village died this month. The case is the largest family cluster known to date.
The WHO and Indonesian health officials are baffled over the source of the infection but genetic sequencing has shown the H5N1 bird flu virus has not mutated, the U.N. agency said on its Web site www.who.int on Tuesday. Nor was there any sign of the virus spreading among other villagers.
"To date, the investigation has found no evidence of spread within the general community and no evidence that efficient human-to-human transmission has occurred," the WHO said.
"Sequencing of all eight gene segments found no evidence of genetic reassortment with human or pig influenza viruses and no evidence of significant mutations," the WHO statement read.
"The human viruses from this cluster are genetically similar to viruses isolated from poultry in North Sumatra during a previous outbreak."
Sick poultry have been the source of bird flu infections for the vast majority of human cases worldwide. Pigs are also susceptible to the virus.
Clusters are looked on with far more suspicion than isolated infections because they raise the possibility the virus might have mutated to transmit efficiently among humans.
That could spark a pandemic, killing millions of people.
The WHO statement came after one of the family members, a 32-year-old father, died on Monday after caring for his ailing son, who had died earlier. The agency said such close contact was considered a possible source of infection.
Closing In
But Firdosi Mehta, acting representative of the WHO in Indonesia, urged against any over-reaction, saying this was not the first cluster that the world has known. He added it was little different from other family clusters that have been documented in the past in Hong Kong, Thailand and Vietnam.
Limited transmissions between people are the result of very close and prolonged contact when the sick person is coughing and probably infectious.
Experts in Kubu Sembilang were doing everything to contain any further spread -- of which there is no sign until now.
"We are going wide, contacting the various contacts, putting on (anti-viral) Tamiflu whoever has had close contact, basically putting family members who have not been affected on Tamiflu as a precaution," he told Reuters in an interview in Jakarta.
"There is active surveillance in the village, fever surveillance to look for any more cases that are occurring outside this immediate family cluster," he said.
But another WHO spokesman said the agency was worried.
"This is the most significant development so far in terms of public health," Peter Cordingley, spokesman for the West Pacific region of the WHO, told Reuters Television in the Philippine capital on Wednesday.
"We have never had a cluster as large as this. We have not had in the past what we have here, which is no explanation as to how these people became infected."
"We can't find sick animals in this community and that worries us," he added.
Bird flu has killed 124 people in 10 countries since it re-emerged in Asia in 2003. It remains essentially a disease in birds and has spread to dozens of countries in wild birds and poultry.
In China, where the virus has been entrenched for the last 10 years, fresh trouble may be brewing as authorities confirmed an outbreak of the H5N1 among wild birds in its remote far-western Qinghai province and Tibet.
About 400 wild birds had been found dead "recently", its state Xinhua news agency said, quoting the Agriculture Ministry.
An outbreak of the H5N1 killed thousands of birds in Qinghai Lake this time last year and this strain of the virus has since turned up in parts of Europe, Africa and the Middle East.
Markets are also nervous about a suspected cluster in Iran.
An Iranian medical official told Reuters on Monday that a 41-year-old man and his 26-year-old sister from the northwestern city of Kermanshah had tested positive for bird flu.
But Health Minister Kamran Lankarani denied this although international health officials are still investigating.
The two siblings were among five members of a family who became sick and the other three remain in the hospital.
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