Monitoring of Influenza and Influenza-Like Viruses in the 2022/2023 and 2023/2024 Epidemic Seasons Using the SENTINEL and NON-SENTINEL Surveillance Systems in Poland

BACKGROUND The SENTINEL influenza surveillance system has been used in Poland since 2004, incorporating both epidemiological and virological monitoring of influenza viruses. SENTINEL works in cooperation with general practitioners, 16 Voivodship Sanitary Epidemiological Stations (VSES), and the National Influenza Centre (NIC). NON-SENTINEL samples are collected from places that do not participate in the SENTINEL program. This enables continuous observation of virological and epidemiological situation in the country. The aim of the study was to conduct a comparative analysis of circulating influenza and influenza-like viruses during the 2022/2023 and 2023/2024 epidemic seasons, as monitored through the SENTINEL and NON-SENTINEL surveillance systems in Poland. MATERIAL AND METHODS The study material consisted of nasal and throat swabs collected by the VSES. Molecular biology methods were employed for virus detection and identification. The analyses were based on data obtained from the SENTINEL system for the 2022/2023 and 2023/2024 epidemic seasons. RESULTS During the 2022/2023 epidemic season, co-dominance of the A/H1N1/pdm09 and A/H3N2/subtypes was noted, whereas the 2023/2024 epidemic season in Europe was dominated by the A/H1N1/pdm09 subtype. Among the influenza-like viruses, SARS-CoV-2 and RSV were the most frequently detected in both epidemic seasons. CONCLUSIONS The influenza surveillance system in Poland enables continuous, weekly monitoring of the epidemiological situation throughout each season. This allows for a rapid response in the event of the emergence of new influenza virus variants. The results obtained as part of influenza surveillance in Poland are consistent with those observed in other European countries.