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Genetic Evidence of Human Transmission of H5N1 in Indonesia
June 23, 2006
Genetic sequencing of a virus sample taken from a 10-year-old boy who died from the H5N1 avian influenza strain showed a minute change that was also found in a virus sample taken from his father who later died from the virus, said Dick Thompson, a spokesman for the United Nations health agency in Geneva.
``We have seen a genetic change that confirms in a laboratory that the virus has moved from one human to another,'' Thompson said in an interview. The change in the virus ``doesn't seem to have any significance in terms of the pathology of the disease or how easily it's transmitted,'' he said.
Human-to-human transmission had previously been suspected as the cause of infection in seven members of the Indonesian family from the island of Sumatra. The cases attracted international attention because they represent the largest reported instance in which avian flu may is likely to have spread among people. They also provide the first evidence of a three-person chain of infection.
The above comments include the first reported genetic link supporting human-to-human transmission of H5N1 bird flu. In the past, the evidence was largely limited to disease onset dates. However, the gaps between the onset date of the index case and other family members has been present in the vast majority of clusters, dating back to the 2003 cluster in the Hong Kong family that had visited Fujian Province.
These data add to the accumulation of evidence for human-to-human transmission within families and between families in Turkey. These clusters have involved several versions of H5N1 including clade 1 and clade 2 and are common.
However, the cases in Karo created the largest and deadliest reported cluster in Indonesia, which highlights minor changes in the H5N1 genes. These changes are not public because the human sequences have been withheld and are sequestered in a private WHO database. Although Indonesia has indicated that the data could be released, only HA and NA sequences from the first confirmed case in Indonesia have been released.
These sequences should be released immediately.