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May 24, (foodconsumer.org) - The World Health Organization said today that limited human-to-human transmission of bird flu might have occurred in an Indonesian family of which six members died of bird flu. Health experts are trying to trace anyone who might have come into close contact with the family.

But the world's health agency said that as of now there has been no evidence to indicate that the H5N1 virus has mutated to a form that is easily transmissible between humans. The problem as far as they are concerned is that a definite source of infection in the family has not been identified. This according to WHO regional spokesman Peter Cordingley is very worrying.

"We have seen clusters in the past and we have seen what was almost certainly (maybe) limited human to human transmission in some cases," he said. "But this is significant because it's the mother of all clusters. It's seven people, six of whom have died and possibly an eighth as well who died before samples could be taken so this is the mother of all clusters."

Six of seven family members in the remote village of Kubu Sembilang in north Sumatra died earlier this month of confirmed bird flu. An eighth family member might also have died of the disease although she was laid to rest before any samples could be taken. This cluster of infections had triggered concern that human-to-human transmission is now possible.

This is also the largest bird flu family cluster and such clusters are looked upon with suspicion by medical experts. Cordingley agreed that the main concern was the source.

"For the first time now we have people dying from this virus but we can find no source of infection outside their own family," he said. "No dead chickens, no dying chickens, basically no animal source at all around them. So we're in a zone we've not been in before which is a large cluster and we don't understand it."

But he added that the WHO had not found any evidence of a mutation in the H5N1 virus. "We've taken samples and we've looked at them and the virus is not mutating…it shows no sign of the ability to transmit more easily between chickens and humans and no sign of any ability to transmit more effectively from human to human," he said.

A possible explanation for the cluster could be that for a long time the family was living in close contact with a person who was in the last stages of the disease. In fact, a WHO statement released Tuesday did allude to this fact.

"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 statement said. "Although human-to-human transmission cannot be ruled out, the search for a possible alternative source of exposure is continuing."

"Sequencing of all eight gene segments found no evidence of genetic re-assortment 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."

But WHO spokeswoman Maria Cheng said that there was no need for any urgent meeting, "Right now it does not look like the task force will need to meet immediately, but this is subject to change depending on what comes out of Indonesia," she said.

Meanwhile in Indonesia, the WHO is tracing people who came into close contact with the infected family members. Firdosi Mehta, acting representative of the WHO in Indonesia told Reuters that they were looking for these people so as to administer Tamiflu as a precautionary measure.

"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. "What is reassuring is two of the human samples from Kubu Sembilang have shown no evidence of reassortment or significant mutations. The lineage of these viruses are very similar to H5N1 viruses from avian specimens from north Sumatra."

No other person in the village is showing symptoms of bird flu. In case of the infected family, they had consumed a pig and chickens for a feast on April 29. Chickens are known to be highly susceptible to the virus.

In fact, health officials have tested several pigs and chickens. Bird flu antibodies were detected in pigs raised by the family. However, nasal swabs taken from the pigs were returned negative.

The WHO has confirmed 218 cases of bird flu worldwide of which 124 have proved fatal to date. The maximum number of deaths has occurred in Vietnam at 42 followed by Indonesia at 33.

The bird flu virus first surfaced in Asia in 1997 and then again resurfaced in 2003. Since then, it has spread rapidly across Asia and Europe as well as Africa. Till now the virus has only been transmitted after close contact with infected birds and coming in contact with saliva, nasal secretions, and feces.

The fear is that if the virus mutates to an easily transmissible form between humans it would trigger a pandemic worldwide. The CDC says that some of the common symptoms of bird flu are fever, cough, sore throat, and muscle aches, eye infections, pneumonia, and severe respiratory diseases. As of now, there has been no evidence that eating cooked poultry will transfer the infection since the virus is heat labile.

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