TUESDAY, Sept. 7 (HealthDay News) -- The median age of individuals affected by 2009 H1N1 influenza was substantially lower than that of individuals affected by 2007/2008 H3N2 influenza; however, the risk of most serious complications was not higher in those with 2009 H1N1 than in those with recent seasonal influenza strains, according to research published in the Sept. 8 issue of the Journal of the American Medical Association.
To compare clinical features and outcomes of the three influenza strains, Edward A. Belongia, M.D., of the Marshfield Clinic Research Foundation in Wisconsin, and colleagues conducted surveillance and 30-day follow-up in 545 2009 H1N1 cases, 221 seasonal H1N1 cases, and 632 H3N2 infections in a 14-ZIP code area in Wisconsin.
The researchers found the median age of patients with 2009 H1N1, seasonal H1N1, and H3N2 to be 10, 11, and 25 years, respectively. Hospital admissions within 30 days occurred in 1.5, 3.7, and 3.1 percent of children and in 4.0, 2.3, and 4.5 percent of adults, respectively. Pneumonia occurred in 2.5, 1.5, and 2.0 percent of children and in 4.0, 2.3, and 1.1 percent of adults with 2009 H1N1, seasonal H1N1, and H3N2, respectively.
"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 authors write.
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