Details on H5N1 Transmission in Pakistan Remain Cloudy
Recombinomics Commentary
December 17, 2007
The Pakistan cases started in mid-November, or possibly earlier, when five family members fell ill in Abbottabad, north of Islamabad. Two of the brothers have died, one of whom was buried before he could be tested for H5N1.
In December, a man and his niece in the same town were found to have H5N1. They are thought to have worked on the same farm as the first family affected. Another man was found to have H5N1 in a nearby town some distance from there. Another case is suspected but not yet confirmed, which would bring the cluster to nine.
The above comments from a Nature story by Declan Butler provide additional detail to the H5N1 cluster(s) in Pakistan, but don’t clear up the many contradictions. Some of the media reports are quite precise on dates, indicating the outbreak links back to a poultry cull on October 21-23. A veterinarian was the index case, who developed symptoms on October 25. Forty samples were collected on or about October 30, and at least four were said to be positive. Two brothers of the index case were students, and they died November 19 and 29. A third brother, a student, also tested positive, but recovered. Two more relatives (originally described as two cousins, but updated to a cousin and another brother), also tested positive, but had mild symptoms.
A sixth brother, residing in Nassau County, New York, was in Pakistan for the funerals. He returned to New York December 5 and tested negative, but WHO media quotes indicated he had mild respiratory disease symptoms, while the report from New York indicated he was asymptomatic. Since he did not return until December 5, it seems likely he was receiving Tamiflu prior to testing, which may have generated a false negative.
Similarly, there is contradictory data on a health care worker. Media reports indicated she tested positive, but was asymptomatic. A subsequent media report indicated she had mild symptoms, but test results were pending.
Thus, key data on disease onset symptoms as well as disease onset dates, remain confused, at best.
Clarification of these issues would be useful. Human-to-human transmission appears to be likely, but the length of the transmission chain and contacts in the chain, remain very much confused.
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