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H5 Wild Bird Flu In Canada Causes More Concern
November 1, 2005
The H5N1 virus, which scientists say kills 100 per cent of the birds it infects......
A wildlife surveillance program that began in August tested 4,800 ducks in six migratory-bird flyways across Canada. Initial results have found an H5-type virus in 28 ducks in Quebec and another five in Manitoba, said Mr. Clark. Results from the other provinces have yet to come back but they, too, are expected to show some H5 infection.
Some form of H5 virus is normally found in about 7.4 per cent of all wild fowl, said Mr. Clark.
The above comments are additional causes for concern. The misconception that H5N1 kills 100% of the birds it affects is widely quoted in the media, but is clearly incorrect. The WHO warning in the fall of 2004 was due to the fact that H5N1 from a fatal human case in Vietnam did not cause death in experimental ducks. Instead the ducks appeared to be healthy and excreted high levels of stable H5N1. This concern was borne out by surveys of waterfowl in Vietnam which showed that 70% were H5N1 positive.
The recent mission report from Russia also detailed about two dozen species that were H5N1 positive when shot down by hunters, indicating that asymptomatic waterfowl was widespread. Further support came from the rapid spread of H5N1 to new areas via migratory birds. After being detected in long range migratory birds in May at Qinghai Lake, H5N1 was then reported for the first time in Russia, Kazakhstan, and Mongolia. Now countries in Europe are reporting H5N1 infections for the first time.
Although some serotype of influenza is found in a significant portion of wild birds, the H5 serotype is not found in 7.4%. In Canada, there have been about 120 deposits at GenBank and only two are H5. One (H5N2) was detected in 1980 and the other (H5N9) was detected in 1966. Thus, there have been no H5 isolates reported in the past 25 years, although that is when most of the deposits from Canada were collected.
The above comments also fail to detail how many of the 4800 birds have been tested or the frequency of H5 in the positive provinces or detail the number of species.
Publication of this data would allow for a more accurate analysis of the H5 data collected thus far.