Casual Contact Transmission of Bird Flu in Thai Binh Vietnam?
Recombinomics Commentary
February 28, 2005
>> Thi Ngoan said she could not be sure of the source of her brother's infection but five days before he was ill he too slaughtered a duck and prepared duck's blood pudding - a delicacy enjoyed all over Vietnam on the eve of Tet, the start of the lunar new year. Thi said she, her brother and her younger sister ate the dish. <<
Although the latest familial cluster from Thai Binh also involves the slaughter of a duck and consumption of duck blood pudding by three family members, the ducks are not the likely source of the H5N1 infection. The familial disease onset dates are bimodal, like the other 10 familial clusters, which makes a common source unlikely.
Like the earlier cluster, disease onset dates do not fall within the usual time frame, which is 2-4 days after exposure. The index case developed symptoms 5 days after the meal, and his sister developed symptoms about 5 days after her brother. Moreover, the third sibling, who also ate the pudding, did not develop any symptoms. In the earlier cluster, the two brothers developed symptoms about 17 days apart and their brother-in-law, who also ate the pudding, did not develop symptoms.
Since the pudding used uncooked blood, the lack of infection in a family member who ate the pudding suggests that neither duck was infected. Thus, like the other cases from Thai Binh, there is not a link to sick poultry, and no independent evidence that the ducks used in the meals were infected with H5N1.
The geographical clustering of the four cases reported in the past few days, coupled with the two earlier familial clusters from Thai Binh, raises the prospect of H5N1 transmission via casual contact. As was noted earlier, the demographics of the patients in the north is more varied than the south. Recent cases have all been from Thai Binh, implicating an environmental source other than the slaughtered and consumed poultry.
Since the H5N1 assay continues to give false negatives in many of the cases involved in these clusters, it would be useful to determine case fatality rates for influenza A patients from Thai Binh.
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