H5N1 Onset Dates in Pakistan Remain Murky
Recombinomics Commentary
December 18, 2007
Ministry of Health spokesman Orya Maqbool Jan Abbasi said the first man to catch avian influenza had been working culling poultry. He recovered but the two men who died were his brothers.
But Abbasi and other health officials said there was no suggestion of human to human transmission.
"Absolutely not," said Health Secretary Khushnood Akhtar Lashari. "The WHO is looking into all the things but whatever we have at the moment there's nothing to suggest that, remotely."
Lashari said the man who had been culling poultry might have inadvertently brought the virus back to his home, where his brothers fell sick.
"He took his equipment along and the suspicion is the virus was in the equipment he was carrying," Lashari said. "These are conjectures. It will be established when they do the sequencing test of the virus."
The above comments raise serious questions regarding the most basic understanding of evidence related to human-to-human transmission of H5N1. The sequencing data does not distinguish between a common source, such as the equipment above, and transmission from the index case, who organized the culling, and infection of four of his brothers, a cousin, and a health care worker.
The most important data sets involve the disease onset dates as well as the contact information, including dates of contact. Human-to-human transmission generates gaps in disease onset dates, which appear to be significant based on reports that the index case developed symptoms on October 25, while the two fatal cases died on November 19 and November 29. Moreover the number of family members involved, along with a positive result for a health care worker, and another familial cluster involving a culler and his daughter or niece, further suggest human-to-human transmission.
Each member in the cluster is expected to be linked to a similar sequence, but the isolation of H5N1 from cluster member is hampered by a reported burial prior to collection of samples, as well as treatment with Tamiflu prior to the collection of samples.
However, the key data points are not the sequences, but the disease onset dates, which should be known almost seven weeks after this disease onset date for the index case.
The comment that there is no evidence to suggest human-to-human transmission is cause for concern, as is the six week delay making the cluster public as well as the continued withholding of disease onset dates.
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