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H5N1 False Negatives in Japan Swans Raise Concerns
Recombinomics Commentary 23:45
May 22, 2008

Among the two swans in Aomori Prefecture was one which was found weakened on April 18 at the premises of a hotel on Towada's southern lake side. It died two days later. The other was one found dead on May 8 in the northern part of Towada.

Both swans tested negative for avian influenza virus in a preliminary examination. But the deadly H5N1 strain was detected later in detailed checks by Tottori University conducted on request by the Environment Ministry, prefectural government officials said.

Separate from the two in Aomori Prefecture, another dead swan was found last Sunday in the village of Sai on the northern tip of the Shimokita Peninsula. It will be sent to Tottori University next week for detailed virus checks, the officials said.

The above comments provide more detail on the two confirmed swans in Aomori as well as a suspect swan in another location at the tip of the Shimokita Peninsula (see satellite map).  These birds were detected via an enhanced surveillance to collect the samples, and repeated testing to detect the H5N1.

The data again highlight the poor sensitivity of the rapid tests.  Dying swans provide ideal samples because viral load is likely to be highest at the time of death, and collection of multiple samples from the recently deceased bird avoids sample degradation linked to decomposition. 

Even though the swan at the hotel was near death, it initially tested negative.  It is likely that the H5N1 in the recent cases will also be Fujian reassortants (clade 2.3.2 / 2.3.4), but detection problems persist, which is why there are so many false negatives when healthy wild birds are tested for Qinghai (clade 2.2) H5N1.

The detection problems raise significant concerns for the US surveillance program, which largely focuses on healthy wild birds, and testing is predominantly on cloacal swabs, which will have a low level of virus.

H5N1 is clearly approaching North America, but the pandemic preparedness of the US surveillance program remains suspect.

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