Clinical Characteristics of Adult Onset RSV Infection During Two Consecutive Winter Seasons

We performed a retrospective study examining adult patients with RSV infection who were diagnosed at our hospital during two consecutive winter seasons, 2011-2012 and 2012-2013; these patients were compared with, adult patients who had been diagnosed as having influenza during the same periods. RSV infection was confirmed by a 4-fold increase in the CF antibody titer, while influenza was diagnosed based on a rapid antigen test. Forty-three patients with RSV infection and pneumonia patients (39 inpatients and 4 outpatients) and 25 patients with influenza and pneumonia (23 inpatients and 2 outpatients) were detected. Overall, 54 patients with RSV infection and 42 patients with influenza, were hospitalized during the two seasons. A history of the influenza vaccination was verified for 48% of the influenza patients with pneumonia and 35% of the non-pneumonia influenza patients who were hospitalized, and neuraminidase inhibitors were used for the treatment of all the influenza patients and 88% of the non-pneumonia influenza patients who were hospitalized. Overall, 5.3% of the adult cases with pneumonia (43/817) during the two seasons were diagnosed as having RSV related illness, and within the peak period, in particular, 14.6% were judged as having RSV pneumonia. Furthermore, 63% of the patients with RSV infection and pneumonia had mixed infections with other common respiratory pathogen, such as Streptococcus pneumoniae, and within the peak period, almost 15% of the patients with pneumonococcal pneumonia were confirmed to have mixed infections that included RSV. In both groups, one-fourth of the patients had been living in nursing homes or had been receibing home medical care. Up to 20% of the RSV pneumonia patients were initially diagnosed as having aspiration pneumonia. We suspect that some of these elderly patients might have developed pneumonia as a result of preceding viral infection or following vomiting or aspiration. The overall clinical picture, such as the mean age, maximum body temperature, hypoxemia, CRP, and WBC, did not differ significantly between the two groups. The 30-day mortality and overall hospital mortality rates were similar in both groups, but the lengths of the hospital stay were significantly longer, and several patients survived but continued to have a reduced activities of daily living score at the time of their discharge in the RSV pneumonia group.