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Commentary
H3N2
Death Cluster In Garden Hill Canada Grows
Recombinomics
Commentary 15:45
December 5, 2010
Dr. Joel Kettner is the Chief Provincial Public Health Officer and he says it's something you can't take lightly.
Dr. Kettner says so far they've had nine positive tests in Winnipeg, one from Parkland, two from Norman and 25 from the Burntwood Regional Health Authority.
The above comments suggest that there has been a third fatal case at Garden Hill (in the Burntwood Regional Health Authority). The above data also breaks down the 37 lab confirmed cases in Manitoba this season, and highlights the concentration at Garden Hill. It also creates a case fatality rate of 12%, assuming the 22 confirmed cases recover. The 12% case fatality rate is extremely high and unusual. Similarly, at least two of the three cases were under 65, which is also unusual for H3N2. Most H3N2 deaths are over 65, which is the case for the first two fatalities in Canada this season (in Ontario).
The ages of the fatal cases are more similar to infections by triple reassortants, including the 2009 H1N1 pandemic. The United States recently issued a pager alert due to two novel influenza cases which were H3N2 triple reassortants (trH3N2). These two cases (in Wisconsin and Pennsylvania) raised the total in the US to five, all of which were reported after the start of the H1N1 pandemic and all were in patients whose age ranged from 10 months to 45 years (22M, 12M, 1F, 10 mo M, 45M).
Similarly, media reports have cited 20 cases who were coughing up blood, which is also unusual for seasonal H3N2. Comments have indicated the H3N2 at Garden Hill is the Perth/16-like H3N2 circulating in Canada, including one isolate from Manitoba. However, it is far from clear that the one Manitoba isolate that has been antigenically characterized is from Garden Hill.
Manitoba reported (Daily Report) the results from the antigenic characterization of their first case, which was from child in Norman, from a sample collected at the end of September. This isolates was antigenically characterized by the National Labs prior to the end of October, but no Manitoba cases were reported in FluWatch prior to the one reported in week 47. Thus, it is likely that the Manitoba antigenic characterization reported in the week 47 FluWatch report was from the child in Norman rather than the fatal case at Garden Hill, which was also reported in the week 47 FluWatch. This interpretation is confirmed by the week 47 report from Manitoba, which indicates only one sample from Manitoba has been antigenically characterized to date.
The antigen characterization data is important because trH3N2 viruses have a human H3 and N2 from the 1990’s. This would create an H3N2 serotype, but would not register as Perth/16-like on an antigenic characterization test (it would register as a "low reactor").
Thus, at this time it is far from clear that there have been any antigen characterization reports for samples collected from Garden Hill this season, which leaves open the possibility that the outbreak is due to trH3N2 rather than Perth/16-like seasonal H3N2, which is widespread in Canada based on antigenic characterization tests of samples collected weeks / months ago.
The outbreak in Garden Hill is recent, so antigenic characterization and sequence data from these samples are critical.
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