A SINGLE – CENTER STUDY ON THE INCIDENCE OF PCR–DETECTED INFLUENZA A/B RNA IN PATIENTS WITH SEVERE ACUTE RESPIRATORY DISEASE (2015-2019)

Influenza virus infection remains the leading cause of morbidity and mortality in the autumn-winter period. Along with insights into circulating virus subtypes and seasonal trends, reliable data on the prevalence of influenza among patients with acute respiratory illnesses is essential for guiding the selection of strains for annual vaccines and for optimizing the planning of immunization programs. Aim. To perform a molecular diagnostic analysis of influenza in patients with severe acute respiratory illness between 2015 and 2019. Methods. A total of 505 patients presenting with symptoms of severe acute respiratory illness and hospitalized at St. Michael’s Clinical Hospital in Kyiv were included in the study. Influenza A and B virus RNA was detected using real-time PCR. Results. During the observation period, 49% of patients tested positive for influenza. The highest positivity rate (86%) was recorded in the 2017–2018 season, with influenza B virus being the predominant strain. In contrast, influenza B virus RNA was not detected during the 2015–2016, 2016–2017, and 2018–2019 seasons. The incidence of influenza A virus during those periods was 28.1%, 50.7%, and 25.4%, respectively. No co-infections were detected. Conclusions. Influenza A virus circulated consistently among patients hospitalized with severe respiratory illness throughout all four seasons from 2015 to 2019. The sharp increase in influenza positivity observed during the 2017–2018 season is attributed to an outbreak of influenza B.