Clinical Features of Hospitalized Cases due to Influenza Virus A Infection in the 2011/2012 Season

Abstract

In the 2011/2012 season, 18 patients were admitted to our hospital due to influenza virus A infection and the number had increased compared to the previous 3 years (average 5.3 patients/year). Therefore we evaluated the clinical characteristics, treatment, and prognosis of hospitalized cases. Although there were many reports on viral pneumonia caused by influenza (H1N1) 2009 among the young population in the 2009/ 2010 season, 16 out of 18 hospitalized patients were over 65 years-old in the 2011/2012 season. Major causes of admission were pneumonia in 8 cases, heart failure in 5 cases and bronchial asthma attack in 3 cases. The average age of 9 patients with pneumonia was higher significantly compared to 9 patients without pneumonia (average age 85.3 ± 10.2 : 71.4 ± 16.1, p < 0.05). Influenza vaccination was performed in 11 patients in total, and 6 out of 9 patients with pneumonia. The interval from illness onset to administration of neuraminidase inhibitors was 1.8 ± 1.1 days in cases with pneumonia and 2.1 ± 1.5 days in cases without pneumonia. Though 17 patients got well, one patient died from aspiration pneumonia after recovering from influenza A infection. In the 2011/2012 season, although many patients who had received vaccination needed to be hospitalized because of influenza A infection, the prognosis was fairly good.