Three H5N1 Familial Clusters in Pakistan
Recombinomics Commentary
December 16, 2007
A third brother was hospitalized for H5N1 infection and also recovered. A fourth brother who lives in the U.S. tested negative for H5N1 after returning to Pakistan for his brother's funeral, Hartl said.
Two cousins, at least one of who is a woman, were positive for H5N1, although they developed only mild symptoms, he said. A man and his niece, who were also involved in culling poultry on either the same or a neighboring farm, have tested positive, Hartl said. The eighth case is a male farm-worker from Mansehra, about 20 kilometers (12 miles) from the other cases, he said.
The above detail on the additional cases who were H5N1 laboratory confirmed and described in the WHO update, define two more familial clusters, in addition to the larger cluster of four brothers were lab confirmed or died with bird flu symptoms. All nine of these patients are linked to culling in October. Seven of these patients match earlier reports which described a culler and his daughter, in addition to a hospitalized male.
The presence of three familial clusters linked to the October culling, provides additional support for a more efficient transmission of H5N1, as well as human to human transmission. This analysis would be more precise if disease onset dates were available, but the deaths of the two brothers on November 19 and 29 strongly support a human-to-human mechanism because of the time gaps, and the two brothers were not involved in the cull and a third positive brother was a school teacher.
In addition, media reports describe an initial positive result in a health care worker linked to the cluster, and there is a media report of symptoms in a hospital visitor, who was linked to a patient hospitalized near the two brothers in isolation. In addition, a fifth brother, who flew to Pakistan for the funerals developed flu-like symptoms as did his son. Although they both tested negative for H5N1, follow-up on convalescent antibody levels on these two primary and secondary contacts would be useful.
The large number of cases described above, as well as familial clusters within the clusters highlights a more efficient transmission of H5N1. Two cases said to have been admitted Saturday have also been described, although the lab confirmation has raised questions about when these two patients were admitted. They are geographically linked to the outbreaks in October and may just be another description of the patients admitted earlier.
However, there are at least nine patients who have died or been lab confirmed, raising concerns of a more efficiently transmitted H5N1 in Pakistan.
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