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Extensive H5N1 Human To Human Transmission In Indonesia?
October 21, 2005
Petersen said preliminary tests showed they had influenza, but the type was unclear. The Health Ministry said it might announce test results later on Friday.
"What we know is that from one clear case in Thailand and probably in other cases there has been close family contact and this is why it could have gone from one person to another," Petersen said.
"It's not what we call extensive human-to-human transmission ... It doesn't mean mutation."
The above comments are in reference to a father and son who were admitted on Wednesday to Sulianti Saroso hospital in Jakarta. The son had handled a neighbor's sick poultry, but his father had not had contact with poultry. Thus, when both were admitted with bird flu symptoms, concern was expressed regarding human-to-human transmission associated with mutation. Since both now have pneumonia and evidence of influenza infection, it likely that the son infected his father with H5N1 bird flu.
However, these familial clusters are not new and although WHO has been slow to acknowledged the fact, the vast majority of the familial clusters involver human-to-human transmission. Now WHO is using a new term, called extensive human-to-human transmission. Since WHO has maintained that the 2005 flu pandemic is a phase 3, which involves only rare human-to-human transmission, the focus on extensive human-to-human transmission may also be an admission that the pandemic has progressed beyond phase 3. When the transmission is sustained, the pandemic has reached the final phase, which is phase 6.
The latest familial clusters will likely be confirmed for both father and son, since they both have tested positive for influenza. This new cluster, however, will add to the evidence that there has been extensive human-to-human transmission. The extent of the human to human transmission can be measured by the frequency of confirmed cases that belong to clusters.
As of today, WHO acknowledges 5 confirmed cases of H5N1 in Indonesia. However, only one of the five is not a member of a known cluster. The test results in Indonesia suggest that those numbers in the next several days will be more slanted toward familial clusters. The nephew of the latest WHO case has tested positive for H5N1 by PCR and will likely be confirmed by Hong Kong. Similarly the latest two cases will also probably be confirmed because they have already tested positive for influenza.
These three new cases would raise the number of confirmed cases to 8, but 7 of the 8 will be linked to four familial cluster involving the eight confirmed, plus an additional three unconfirmed cases.
The fact that almost all confirmed cases are coming from familial clusters I cause for concern regarding extensive human-to-human transmission. This concern is increased by the geographical clustering of confirmed and suspected cases in and around Bekasi (see Jakarta map). Geographical clustering is a sign of easy transmission of H5N1 to humans, as is the large number of zoo visitors who developed bird flu symptoms, some of whom also had H5N1 antibodies.
Thus, although human-to-human transmission in family has been noted in Vietnam, Thailand, Cambodia, and Indonesia, the human-to-human transmission in Indonesia now appears to be extensive human ti human transmission.