Commentary
Recombinomics Commentary 19:46
January 17, 2009
The girl, surnamed Peng, was found ill on Jan. 7 in the central Hunan Province.
The above comments describe the most recent H5N1 confirmed case in China. She was infected right after the patient in Beijing died, who was infected a couple weeks after the outbreaks Jiangsu. All three incidents (see updated map) involved H5N1 confirmed hosts in the absence of dead poultry.
The outbreaks in Jiangsu were detected during routine surveillance. As noted in the OIE report, there were no dead birds. The H5N1 in the Jiangsu outbreaks was clade 7. Clade 7 is quite distinct from clade 1 and clade 2 which are the two clades that have accounted for the vast majority of human cases and outbreaks. However, clade 7 had caused the first confirmed case in China in Beijing in 2003. It has been reported in poultry outbreaks in northern China are provinces near Beijing, as well as Hunan province.
The history of outbreaks and the temporal relationship to the Beijing case suggest clade 7 may have been involved in the Beijing infection(s). The same is true for the Hunan case.
Clade 7 is cause for concern because it has caused at least one human case previously and was in asymptomatic birds in Jiangsu. Moreover, it has caused problems previously in vaccinated flocks. The genetic differences between clade 7 and clade 1 or 2 can produce vaccine mismatches which generate asymptomatic birds which shed H5N1 that can infect other birds and humans. This creates conditions fro silent transmission in birds and cases that have no clear linkage to dying poultry.
China has not filed any OIE reports since the Jiangsu outbreak in December, suggesting H5N1 was not detected in poultry culled in the Beijing area. Detecting H5N1 in asymptomatic birds is difficult, so the absence of H5N1 positive birds does not necessarily signal the absence of H5N1.
The widespread detection of H5N1 in China in the absence of dead or dying poultry is cause for concern.
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