POST-COVID RESURGENCE OF RESPIRATORY VIRUS INFECTIONS IN PALERMO UNIVERSITY HOSPITAL

Introduction/Objective: During COVID-19 pandemic the spread of respiratory viruses other than SARS- CoV-2 has been limited by social distancing and use of personal protective equipment. However, viral respiratory infections were able to resurge in the post-pandemic period. This study investigated the prevalence of respiratory viruses among patients hospitalized with acute respiratory symptoms during two consecutive winter epidemic seasons: 2022/23 and 2023/24. Material and Methods: A total of 637 patients hospitalized at Policlinico “Paolo Giaccone” University Hospital in Palermo, Italy, from 1st September 2022 to 29th March 2024, were investigated for respiratory virological infections, testing 633 nasopharyngeal swabs and 35 bronchoalveolar lavages (BAL). In particular, from September 2022 to February 2023, 226 patients, negative to molecular test for SARS-CoV-2, were tested using Allplex Respiratory Panels 1-3 (Seegene, South Korea), while, since 1st March 2023 411 patients were tested with the new RV Master Assay (Seegene, South Korea) which simultaneously detects SARS-CoV-2 with seven other major respiratory viruses: influenza A (Flu A), influenza B (Flu B), respiratory syncytial virus (RSV), metapneumovirus (MPV), adenovirus (AdV), rhinovirus (HRV), and Parainfluenza virus (PIV). Results: A total of 212 patients (33.3%) tested positive for at least one respiratory virus in nasopharyngeal swabs (31.3%; 198/633) and/or BAL (51.4%; 18/35). A single infection was detected in 184 patients, while 28 patients (13.2%) were coinfected. The mean age of patients was 68 years, 295 were female (46.3%) and 342 were male (53.6%). Patients with viral respiratory infections were admitted to different hospital wards, including Internal Medicine (56.6%), Infectious Diseases (12.7%), Geriatrics (9.4%), Pneumology (9%), Intensive Care (7%), and others (5.2%). Among respiratory viruses, HRV was mainly detected (33.9%), followed by Flu A (19.4%), RSV (11%), AdV (7%), MPV (6%), PIV (5.2%), and other respiratory viruses (12%). Since March 2023, SARS-CoV-2 was detected in 10 patients out of 269 (3.7%). Peak circulation of HRV was observed in January and March, while influenza was detected in December, RSV in January, and MPV mainly in January and March. Conclusions: Circulation of respiratory viruses is increasing in the post-pandemic period. The use of syndromic molecular panels allowed to ascertain that 33.3% of hospitalized patients had viral infections, with HRV accounting for most of the infections. During the COVID-19 pandemic the reduced circulation of respiratory viruses may have led to an immunity debt towards respiratory viruses, resulting in severe respiratory infections in the post-pandemic period, particularly among vulnerable groups such as the elderly. The etiological diagnosis of viral infections is crucial for the proper management of patients, including therapeutic treatment and isolation, but also to monitor and reduce the spread of pathogens and safeguard public health.