It however maintained that human contagion cannot be ruled out in the family cluster of the avian flu in Indonesia.
So far there has been no evidence that efficient human-to-human transmission has occurred, a development which would signal a potentially dangerous mutation of virus into a deadly pandemic that has the potential of killing millions worldwide, the World Health Organisation said yesterday.
Meanwhile, WHO and Indonesian health ministry have intensified probe following the possibility that six members of a family in North Sumatra who died of bird flu could be the case of human-to-human infection as investigators were unable to find contact with infected birds of all those who caught the deadly virus. A seventh member has also been infected.
Priority, WHO said, is now being given to the search for additional cases of the illness in other family members, close contacts, and the general community after seven members of an extended family became infected with the H5N1 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.
Over 200 million birds have died worldwide from either the virus or preventive culling and there have so far been only 218 known human cases, 124 of them fatal, since the current outbreak started in South East Asia in December 2003, and these have been ascribed to contact with infected birds.