The first member of the family in North Sumatra to contract the virus died of the disease on 4 May. By 22 May, another seven members of the family had been confirmed as H5N1 cases and six of them had died.
The WHO said last week that the source of this outbreak of the virus was unknown.
Although it had found no evidence so far of the virus spreading in the general community, human-to-human transmission of the bird flu virus could not be ruled out, it said.