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WHO Confirms H5N1 Cluster In Indonesia
May 17, 2006
"There are six confirmations. One from Surabaya and five from Medan. One from Medan is still alive," said Sari Setiogi, the WHO's Indonesia spokeswoman.
An outbreak of H5N1 bird flu involving up to eight members of a family at Medan in North Sumatra province has worried health agencies around the world but a Health Ministry official said on Wednesday it was not a case of human-to-human transmission.
The WHO confirmation of 5 Medan cases is not a surprise. Virtually all cases that test positive in Indonesia are confirmed by the WHO associated lab in Hong Kong. There are eight members in the cluster and six have died. In local testing, it appears that only one of the eight has tested negative, although false negatives are common. Since one of the surviving members of the clusters has tested positive, the size of the cluster is at least seven members, including six fatalities.
The disease onset date of the index case is April 27, indicating that this cluster, like the majority of H5N1 clusters is another example of human-to-human transmission. Local media has mentioned a family gathering, but this is yet another mechanism for the creation of familial clusters. This is similar to the large cluster in Turkey, which was precede by a family gathering between cousins. The index case had developed symptoms prior to the gathering, and many family members developed symptoms after the gathering.
Although these large clusters have not generated a pandemic thus far, the large clusters have demonstrated a more efficient transmission to humans, and the presence of an index case with symptoms strongly implicates human-to-human transmission.
The first H5N1 confirmed case in Indonesia was also a cluster. The sequence of the HA from the father in that cluster has been made public, and it has a novel cleavage site (RESRRKKR). Although these have now been many sequences from bird isolates released, none have had this cleavage site, nor have any other HA sequences at GenBank.
The failure to release additional human sequences raises concerns that these sequences do not support a poultry origin, but such data is being withheld. WHO maintains a large private database and those sequences should be released immediately.