VIROLOGICAL SURVEILLANCE OF RESPIRATORY VIRUSES DURINGTHE 2022-2023 FLU SEASON IN ROMANIA

Acute respiratory infections are a major public health concern. They are difficult to control and affect a large part of the population. This respiratory surveillance report summarizes key insights into circulating respiratory viruses, including influenza, SARS-CoV-2, respiratory syncytial virus (RSV), parainfluenza virus (PIV), human metapneumovirus (hMPV), rhinovirus (RV), coronaviruses (hCoV), adenoviruses (AdV), enteroviruses (EV), and bocaviruses (BoV) during the 2022-2023 season in Romania. From week 40/2022, 5103 clinical specimens were collected and sent to the National Influenza Centre in Cantacuzino NMMIRD. Specific genetic materials of respiratory viruses were detected using the real-time molecular polymerase chain reaction (RT-PCR) method using commercial kits and in-house optimized PCR tests. Six hundred and ninety-two clinical specimens were identified with PCR-confirmed influenza type A and B (A/H1pdm09, A/H3, and B/Victoria), and 106 were detected for other respiratory viruses (hCoV, hMPV, RSV, RV, AdV, PIV4, and EV) between October 2022 and April 2023. Influenza A predominated at the start of the season, with both subtypes (H1pdm09 and H3) co-circulating, but as the season progressed, the influenza B/ Victoria lineage viruses became circulating at higher proportions. The highest infection rate was in individuals aged 15-49 (37%). The 2022-2023 influenza season marked the return of influenza virus activity to almost pre-pandemic levels in Romania. Virus characterization data determine the similarity of circulating viruses to the influenza vaccine components. Surveillance is critical during flu season. In addition to the dominant flu virus, other noninfluenza viruses have been identified.