Clinical Differences in Hospitalized Adult Influenza Patients between the A (H1N1) pdm09 and the A (H3N2) Seasons in Japan

Nozomi Oikawa and Masafumi Sek

Abstract

To determine the differences in the clinical features of hospitalized elderly patients with influenza between the A (H1N1) pdm09 and the A (H3N2)-dominant seasons, 12 adult patients (mean age, 76.5 years) with influenza who were hospitalized during the 2015-2016 A (H1N1) pdm09-dominant season were compared with 26 adult patients (mean age, 82.5 years) with influenza who were hospitalized during the 2016-2017 A (H3N2)-dominant season. Compared with the A (H3N2)-dominant 2016-2017 season, the A (H1N1) pdm09-dominant 2015-2016 season had fewer non-survivors, but had significantly fewer patients who required oxygenation/respirator support and intravenous anti-influenza agents, such as peramivir. Among the severe patients who received oxygenation/respirator support, the outcomes were better in the A (H3N2)-dominant 2016-2017 season than in the A (H1N1) pdm09-dominant 2015-2016 season. The pneumonia types and detected bacteria did not differ between the two seasons, but the use of sulbactam/ampicillin was more frequent in the A (H1N1) pdm09-dominant 2015-2016 season than in the A (H3N2)-dominant 2016-2017 season. These data suggest that peramivir treatment and oxygenation/respirator support, but not sulbactam/ampicillin administration, may improve the outcome of severe elderly patients hospitalized for influenza, especially the A (H3N2) type.