Clinical comparison of pandemic H1N1 vs other influenza infections

January 01, 0001

Clinical comparison of pandemic H1N1 vs other influenza infections

The clinical characteristics of pandemic 2009 H1N1 influenza illness have not been compared directly with infections caused by other influenza A strains. These US researchers compared clinical features and outcomes for 2009 pandemic H1N1, seasonal H1N1, and H3N2 influenza in a population-based cohort in Wisconsin (n=6874). Patients with influenza like illness of fewer than 8 days' duration were screened for eligibility during medical encounter. Consenting patients were interviewed and tested for influenza A during the 2007-2008 and 2008-2009 influenza seasons and from May to November 2009.

The researchers report: "We identified 545 2009 H1N1, 221 seasonal H1N1, and 632 H3N2 infections. The median ages of infected participants were 10, 11, and 25 years, respectively. Hospital admission occurred within 30 days for 6 of 395 children with 2009 H1N1 (1.5%), 5 of 135 with seasonal H1N1 (3.7%), and 8 of 255 with H3N2 (3.1%; 95%). Among adults, hospital admission occurred in 6 of 150 with 2009 H1N1 (4.0%), 2 of 86 with seasonal H1N1 (2.3%), and 17 of 377 with H3N2 (4.5%). Pneumonia occurred in 10 children with 2009 H1N1 (2.5%), 2 with seasonal H1N1 (1.5%), and 5 with H3N2 (2.0%). Among adults, pneumonia occurred in 6 with 2009 H1N1 (4.0%), 2 with seasonal H1N1 (2.3%), and 4 with H3N2 (1.1%)."

The researchers concluded: "In this population, individuals with 2009 H1N1 infection were younger than those with H3N2. The risk of most serious complications was not elevated in adults or children with 2009 H1N1 compared with recent seasonal strains."

The study finds that pandemic H1N1 influenza in general did not have more complications than other influenza infections.

For the full abstract, click here.

JAMA 304(10):1091-1098, 8 September 2010
© 2010 American Medical Association
Clinical Characteristics and 30-Day Outcomes for Influenza A 2009 (H1N1), 2008-2009 (H1N1), and 2007-2008 (H3N2) Infections. Edward A. Belongia, Stephanie A. Irving, Stephen C. Waring, et al.

Category: R. Respiratory. Keywords: influenza, H1N1, pandemic, characteristics, complications, population based cohort, journal watch.
Synopsis edited by Dr Paul Schaefer, Toledo, Ohio. Posted on Global Family Doctor 24 September 2010

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