Electronic letters to:

Original Article:
Sean O'Riordan, Michelle Barton, Yvonne Yau, Stanley E Read, Upton Allen, and Dat Tran
Risk factors and outcomes among children admitted to hospital with pandemic H1N1 influenza
CMAJ 2009; 0: cmaj.091724v1 [Abstract]
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Electronic letters published:

[Read eLetter] The severity of 2009 pandemic H1N1 influenza
Nevio Cimolai MD, FRCP(C)   (14 January 2010)

The severity of 2009 pandemic H1N1 influenza 14 January 2010
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Nevio Cimolai MD, FRCP(C),
Children's and Women's Health Centre of BC
Professor, The University of British Columbia

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Re: The severity of 2009 pandemic H1N1 influenza

ncimolai{at}interchange.ubc.ca Nevio Cimolai MD, FRCP(C)

Timely information in regards to the 2009 pandemic influenza A (H1N1) would have been welcome by both the medical community and the public. Although it is expected that reports such as that from O’Riordan et al. would eventually emerge in Canada, it was apparent to many front-line general practitioners that the patients suffering from this infection and who were returning from Mexico to Canada in April and May, 2009 were not suffering an overly aggressive illness.

O’Riordan et al.’s findings are consistent with the above, but now in the scientific eye, limitations of such research are important to recognize. While challenging to find a reasonable comparison group, the retrospective selection of illnesses is likely to draw some attention. For example, the choice of a comparator group based solely on antigen type A is of curiosity. The pooling of several influenza A strain related illnesses over multiple years is likely to soften the appearance of any more severe illnesses from an individual strain in a given year. There is no scientific reason to believe that a multi-year pooling of illnesses for either influenza A or B would be any different. The considerable media attention to this year’s pandemic might also have prompted patients to seek emergency and/or institutional care earlier. Patient referrals from other centres to the Hospital for Sick Children in Toronto are likely in themselves to be subject to considerable year-to-year bias. It is also not apparent form the paper that significant differences in age between pandemic and seasonal infection groups were to be adjusted prior to the assessment for severity of illness and outcome.

Having access to early and timely data if appropriately collated and analyzed would have been of potential value to all. In future planning for potential pandemics, acquisition of such data from academic centres and public health could be speedily groomed, analyzed, and disseminated in Canada. Support for such endeavours is well within the mandate of our national health agencies. We will have plenty of years ahead of influenza activity in order to give such data gathering the preliminary assessments that are required to have an excellent model well in place ahead of time.

Conflict of Interest:

None declared