Title : Current topics of adult COVID-19, Influenza, and RS virus patients in Japan
Abstract:
Background: Respiratory syncytial virus (RSV) is a pathogenic respiratory virus that is considered to affect not only children but also adults, especially elderly persons aged ≥65 years. However, in Japan, the annual epidemic situation and severity of RSV infections in these adults have not yet been clarified, especially during the COVID-19 pandemic. In addition, COVID-19-related pneumonia was initially rare, though influenza-related pneumonia is well known as a severe complication of influenza. However, COVID-19-related pneumonia may be increasing since the omicron variant of COVID-19 appeared.
Methods: The epidemic of RSV, especially the number of adults with RSV infection during the COVID-19 period, was retrospectively analyzed. In addition, the clinical features of patients aged ≥65 years (older group) and those aged ≤64 years (younger group) were compared. Furthermore, the clinical differences between COVID-19-related and influenza-related pneumonia patients were retrospectively investigated in patients hospitalized from January 2022 to December 2023.
Results: A total of 58 patients were found to have RSV infections from April to August 2021. Ten were adults, and five each were detected in June and July, respectively. Of the 10 adult patients, three were in the older group and were more often infected by their grandchildren, and seven were in the younger group. All older patients had underlying diseases, including diabetes mellitus. In addition, the older group showed more severe inflammation, such as increased white blood cell counts and C-reactive protein levels, and received antibiotic therapy, whereas no antibiotics were used for the younger group. Two of the three older patients were admitted to our hospital, but survived. In addition, COVID-19-related and influenza-related pneumonias were found in 46 of 285 (15.8%) and 6 of 12 (50.0%) patients, respectively (p<0.001). Their mean ages were 75.5 (45-93) years and 53.8 (19-73) years in COVID-19-related and influenza-related pneumonia cases, respectively (p=0.002). Aspiration pneumonia was more common in COVID-19-related pneumonia (28/46=60.9%) than in influenza-related pneumonia patients, and it was treated by sulbactam/ampicillin (31/46=67.4%). The influenza-related pneumonia patients were more often infected in the work place (2/6=33.3%) and not vaccinated (4/6=66.7%), compared with COVID-19-related patients. Death occurred in 7 of 46 (15.2%) COVID-19 patients, but none of 6 influenza-infected patients died.
Conclusion: These data suggest that RSV infection in adult patients was related to the increase in pediatric RSV patients and that the infection season had shifted to summer, similar to other countries. Among the adult RSV patients, those aged ≥65 years were more often infected by their grandchildren and received antibiotics because of their more severe inflammatory status than patients aged ≤64 years during the COVID-19 pandemic in Japan.
Furthermore, COVID-19-related pneumonia presented as aspiration pneumonia in older patients, although influenza-related pneumonia was more common in younger and non-vaccinated patients and might be associated with immune mechanisms during the omicron variant surge era.
