Tamiflu Blanket and H5N1 False Negatives in Pakistan
Recombinomics Commentary
December 17, 2007
Four brothers and a cousin from a family in Peshawar, near the border with Afghanistan, were among those who tested positive for the virus during the past three weeks, WHO spokesman Gregory Hartl said.
While almost all human H5N1 cases confirmed by WHO have shown severe symptoms, such as pneumonia, in Pakistan at least two people had only mild disease. Anwar said this was probably because the patients had begun taking Roche Holding AG's Tamiflu one to two days before being tested, and the medicine reduced the severity of symptoms.
The above comments describe the use of a Tamiflu blanket in the recent H5N1 outbreak in Pakistan. Although this approach certainly has the potential for suppressing the spread of H5N1, collection of samples 1-2 after the start of treatment can generate false negatives.
This is a possibility for the sixth brother (38M), who lives in Nassau County, New York. As noted above, four of the brothers tested positive, and the fifth brother died with bird flu symptoms, so all five brothers of the New York resident were H5N1 infected. If the New York resident was in Pakistan for both funerals, and funerals followed the November 19 and 29 deaths, then the exposure period was extensive. Moreover, it is likely that he had received prophylactic Tamiflu treatment in Pakistan, which may have generated false negatives in tests in the United States conducted by New York and the CDC.
Similarly, the spread of H5N1 in Pakistan may have been masked by the Tamiflu blanket. Testing of contacts, including the brother in New York would be useful, to determine how efficiently the H5N1 in Pakistan infects contacts. Clearly, the infection of five brothers in the same family is an H5N1 cluster high, and strongly supports human-to-human transmission. This transmission may have also extended to the health care worker, who was also said to be positive, and who also was a likely recipient of prophylactic Tamiflu prior to collection of samples.
Media reports have indicated the brother from New York was H5N1 positive in Pakistan, was negative in nthe US but symptomatic, and was negative in teh US and asymptomatic. Similar mutually exclusive descriptions for the health care worker have also been published in media reports.
Accurate information on disease onset dates and disease symptoms would be useful.
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