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.