Jun 23, 2006 (CIDRAP News) – The recent family cluster of H5N1 avian influenza cases in Indonesia marks the first time laboratory tests confirmed human-to-human transmission, the World Health Organization (WHO) told reporters today.
According to news reports, WHO officials said the virus mutated slightly when it infected a 10-year-old boy, and he passed the altered virus on to his father. Detection of the altered strain in both the boy and his father was evidence of direct transmission.
The mutation did not make the virus more transmissible, and the boy's father, who died of the illness, did not pass it on to anyone else, WHO officials were quoted as saying.
"We've never really had a fingerprint to confirm human-to-human transmission like we had here," said WHO spokesman Dick Thompson, as reported by Agence France-Presse (AFP) today.
Human-to-human transmission has been suspected in a number of previous family case clusters but has never been confirmed by lab tests. Previously, either there were no samples available to test, or the virus in the patients was the same as in local poultry, according to an International Herald Tribune report today.
The family cluster last month in North Sumatra involved seven confirmed cases, six of them fatal. The cluster is believed to have started with a 37-year-old woman who died and was buried without being tested for the disease. Officials believe she caught the virus from poultry and passed it on to other family members.
WHO report not released to press
The WHO discussed some of its findings concerning the cluster at the end of a 3-day meeting in Jakarta today, according to reports. The agency presented a report on the cluster to the Indonesian government without releasing it to the news media. But the Associated Press (AP) said it had obtained a copy.
According to the International Herald Tribune report, the first five family members who got sick had identical strains of H5N1, one that is common in animals in Indonesia. But the virus mutated slightly in the 10-year-old boy.
Thompson described the virus as "slightly mutated, but in a way that viruses commonly mutate," the story said. "But that didn't make it more transmissible or cause more severe disease," he said.
Health officials have previously described the case cluster as the first instance of a probable three-person chain of transmission (two generations of transmission).
Tim Uyeki of the US Centers for Disease Control and Prevention said the findings about the boy passing the virus to his father provide evidence of that occurrence, according to an AP report published today.
Officials gave no details today on the mutation that was observed in the H5N1 strain found in the boy and his father.
According to Bloomberg news, a 7-page summary report on the investigation said genetic analyses of viruses from the family cluster showed no evidence of reassortment, or combination of avian and human flu viruses.
Keiji Fukuda, director of the WHO's global influenza program, told reporters that the case cluster prompted the WHO to consider whether to move into a pandemic alert, according to a Reuters report today.
"The answer is clearly no," he said. "We see no evidence of the start of pandemic influenza."
Avian flu widespread in Indonesia
However, H5N1 avian flu is widespread in Indonesia, experts said in a statement released at the end of the Jakarta meeting. The statement said the government should focus on detection of human case clusters, according to the Reuters report.
"Highly pathogenic H5N1 avian influenza is widespread and well established in Indonesia but the full extent is unknown," the statement said. "It is believed that large numbers of animal infections are undetected.
"The public is still lacking basic knowledge of the risks to their poultry and themselves and therefore their understanding of control methods in poultry and how to protect themselves is minimal."
Jeff Mariner, a Tufts University researcher who attended the meeting, said avian flu is more pervasive in Indonesia's poultry than previously thought, according to an AP story.
Mariner is coordinating a United Nations Food and Agriculture Organization effort to train local avian flu surveillance teams. In 12 pilot districts on Java Island, the teams detected 78 poultry outbreaks from January through May, with about one out of every 10 interviews revealing an outbreak, Mariner told the AP.
Because of a lack of personnel, the surveillance covered only about a third of each district, he said.