Quang Binh Bird Flu Cluster Index Case Commentary
Recombinomics Commentary
March 22, 2005
>> It is still being asserted that the death of the elder sister of the H5N1 virus-infected 5-year-old boy may have been due to avian influenza, although this was presumably not suspected at the time, as no diagnostic samples were collected. The evidence for avian influenza virus infection is not compelling, since the death of the elder sister occurred prior to the illness of the brother, and apparently a younger sister was left unscathed. - Mod.CP] <<
The above commentary is at odds with the long history of bird flu familial clusters in Vietnam, Thailand, and Cambodia, where no sample was tested from the index case, and one or two family members were then confirmed to be H5N1 positive.
The most cited example is the familial cluster in Thailand which was described in the New England Journal of Medicine. The index case was misdiagnosed as having dengue hemorrhagic fever. Although a serum sample was sent to the dengue fever lab for testing, the sample was collected too soon after infection to have H5N1 antibodies. The index case was cremated without any laboratory confirmation of H5N1 infection. There certainly was reason to suspect bird flu because there had been outbreaks in poultry in the area and the index case had buried a chicken that had died. Similarly, there was no sample collected from her mother, who also died with bird flu symptoms. Her body had been embalmed and was about to be cremated when investigators, who were fortuitously alerted, were able to collect fixed tissues and obtain H5N1 sequences.
There was a similar cluster in Thai Binh in January, 2004 when a groom developed bird flu symptoms. No sample was collected but both sisters who tended to him developed symptoms on the same day, went in the hospital the same day, and died within 1 hour of each other, Both tested positive for H5N1, although initial tests were inconclusive.
This scenario was repeated in July of 2004 for a Hau Giang familial cluster. Two cousins developed bird flu symptoms in a region that had dying chickens and prior confirmed infections. No samples were collected from either cousin, but the older sister cared for one of the cousins and developed symptoms and was confirmed to be H5N1 positive.
This sequence was repeated in the familial cluster in Cambodia at the beginning of this year. The index case collected dead poultry in the village and developed bird flu symptoms. No sample was collected but after he died his sister developed symptoms. She was subsequently confirmed to be H5N1 positive.
Thus, there has been a long history of index cases that had exposure to sick poultry, developed symptoms, and did not have samples collected for H5N1 testing. The examples above are from high profile clusters, and indeed would have probably gone unnoticed had not other family members developed symptoms. All of these index cases died with bird flu symptoms, and all secondary cases except the aunt in Thailand died after testing positive for H5N1.
The index case of the Quang Binh cluster ate sick chickens and died with bird flu symptoms without sample collection. Her sibling later developed symptoms and was H5N1 positive.
To conclude that the evidence for the index case in Quang Binh is not compelling, in part because the index case developed symptoms before the secondary case, is an embarrassing commentary that has no place in a widely read publication of an infectious disease society.
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