WHO concerns about human bird flu concentration in Indonesia

The U.N. health agency on Wednesday described the deaths of six Indonesian family members from bird flu as the most important development in the spread of the virus since 2003, saying it was concerned about the size of the cluster and confusion over its source. "We have a team down there, they are examining what is going on and they can't find an animal source of this infection," said Peter Cordingley, spokesman for the Western Pacific region of the World Health Organization.

"This is the first time that we've been completely stumped" by a source for the infection, he said. Six of the seven people in an extended family in northern Sumatra who caught the disease have died, the most recent on Monday, in one of the largest human clusters of H5N1 ever reported. WHO is investigating whether bird flu was passed from person to person, but said Wednesday there was no evidence the virus had mutated to a form that was spreading more easily between humans, a scenario that could spark a global pandemic killing millions. There also was no indication it had infected anyone outside the family.

"No matter what's going on at this stage, it's a limited transmission between members of the same family," Cordingley said from Manila , describing the Sumatra case as the most important development since the H5N1 virus started ravaging poultry stocks across Asia three years ago. Isolated cases of the virus jumping from one human to another have been documented including one in Thailand involving a mother and child but such cases do not mean a pandemic flu strain has emerged.

"What we are looking out for is any sign of this virus going outside of this family cluster into the general community, that would be very worrying," Cordingley said. "We haven't seen any signs of that yet." Bird flu has killed 124 people worldwide, more than a quarter of them in Indonesia , which has come under fire in recent months for doing too little to slow the spread of the disease. Most human cases have been traced to contact with infected poultry.

Steven Bjorge, the WHO team leader in the village of Kubu Sembelang , said the virus that infected the family members was genetically the same as the one found circulating in the area earlier. Test are still being carried out on poultry in the village. Peter Roeder, an animal health expert from the U.N. Food and Agriculture Organization in Rome , said tests so far had been negative for the virus, but antibodies were found in some specimens taken from chickens and ducks.

It's unclear, however, whether they were infected at the time the family members fell ill. They could have been sickened much earlier or developed antibodies after vaccination, he said, adding that no immunization records were available. Dead poultry was also found in an area outside the village, but test results have not yet come back, said Roeder, who has worked closely with Indonesia to strengthen poultry surveillance and response to bird flu outbreaks.

The first Sumatra family member believed to be infected worked as a vegetable vendor in a market where live poultry was sold, Bjorge said, but experts were still trying to determine if that was where she became infected. The woman, who died May 4, was never tested for the H5N1 virus, but WHO considers her part of the family cluster. The woman's 25-year-old brother is the only family member still living after contracting the virus.

"All confirmed cases in the cluster can be directly linked to close and prolonged exposure to a patient during a phase of severe illness," the WHO said in a statement on its Web site. Bjorge said some samples have been taken from villagers, but that local authorities have resisted working with outside health experts. WHO has enlisted local villagers to help monitor the village for anyone experiencing flu-like symptoms. If anyone is found to have even mild symptoms, they will be quarantined and given the anti-bird flu drug Tamiflu, he said, reports the AP.