Human Transmission of Bird Flu in Atypical Patients
Recombinomics Commentary
March 8, 2005
>> The seven people, all from southern Vietnam, didn't have clinical or epidemiological factors typical of previous bird-flu cases, the institute official said. One patient had tuberculosis. <<
The seven false negatives were all from southern Vietnam, which may explain why all confirmed H5N1 cases in the south have died. The bird flu test may only detect the most severe cases, raising questions about how many H5N1 cases were missed.
Since the false negatives also did not have clinical or epidemiological factors typical of previous bird flu cases, it seems that they would not have had a history of contact with poultry, increasing the likelihood of undetected human-to-human transmission. As was seen in the familial clusters, even when index cases were from provinces with dying poultry or a history of prior H5N1 infections, the patients with clear bird flu symptoms were not tested.
These new cases indicate that many H5N1 patients are either not being tested because they do not have "typical" symptoms, or they are falsely testing negative.
Earlier comments from officials in Vietnam had mentioned complex cases in Vietnam and Cambodia, suggesting a much wider spread of the H5N1 virus. The false negatives in southern Vietnam may explain the failure to detect any human cases this season in Thailand, even in cases that have handled dead chickens, have lung involvement, and are positive for influenza A.
The reports of additional false negatives in non-fatal cases combined with an atypical clinical presentation or epidemiological profile strongly suggests that there has been much more human-to-human transmission of H5N1.
The H5N1 spread has probably gone beyond the borders of Vietnam, Thailand, and Cambodia.
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