More comments on the H5 positive birds from Canada

I believe Henry Niman, who maintains the Recombinomics blog, is overstating the significance of the recent finding of H5 influenza in wild birds in Manitoba and Quebec.  His comments are here, here, and here.

His main point is that H5 subtypes are hardly ever isolated from wild birds in Canada, and cites only 2 deposits in Genbank as evidence for this statement.  Therefore, he argues " ... H5 serotypes in Canada a rare, raising concerns that the 33 H5 isolates are HPAI H5N1."

I disagree with him.  Although rare, low pathogenic H5 avian influenzas have been isolated several times from migratory birds in Canada, forming 2-3% of all isolations of influenza from wild ducks and shorebirds in North America (Webster et al. 1992). 

The Canadian study is not yet complete so we don't know how many samples have been taken and what other serotypes have been found - we just don't have all the information to put these isolations into context yet.  When the study is complete, we may find that the handful of H5 positives reported by the Canadian government is perfectly in line with what would be expected from previous surveys.  Ultimately, determining the neuraminidase (N) subtype, followed by pathogenicity trials to determine if this is high or low pathogenic influenza, is necessary to settle question.

There is nothing to be gained by making alarmist and speculative statements from less than all the data.  The Canadians should be commended for conducting this study and reporting the results in a timely, open manner.  We need more baseline data like these to put the emergence of new viruses in perspective.

Damien