Serological Monitoring of Pandemic Influenza Virus Markers in the Russian Federation in 2021–2023

Abstract

State Scientific Center of Virology and Biotechnology “Vector” has been monitoring highly pathogenic influenza since 2005.The aim of this work was to track the markers of highly pathogenic influenza in the blood sera of people who had a contact with infected and/or deceased birds, as well as of residents from regions where emergence of new variants of influenza A virus is most likely to occur.Materials and methods. Sera were studied using hemagglutination inhibition test (HI test). HI-positive sera were subjected to virus neutralization reaction.Results and discussion. In 2021, 2076 blood serum samples from 19 regions of Russia were collected. Only 7 samples demonstrated significant titers in HI test with A/H5N8 viruses. In 2022, 1620 blood serum samples from 23 regions were obtained; 25 of them were positive for influenza А/H5N8 and А/H5N1 viruses. In 2023 (January-August), 3335 serum samples from 31 regions of the Russian Federation were collected. 28 samples were positive for influenza А/H5N8 and А/H5N1 viruses. Furthermore, we monitored blood sera for low-pathogenic A/H9N2 virus. The number of positive samples in 2021 was lower than 1 % (13 out of 2076); in 2022, it reached 5 % (81 out of 1620); in 2023, the share was lower than 1 % (31 out of 3335). The data obtained suggest indirectly that currently there is no stable circulation of zoonotic influenza A/H5N8 and A/H5N1 viruses in Russia. Influenza viruses A/H9N2 have widely spread in many countries of the world and actively participate in evolution of highly pathogenic influenza A/H5Nx viruses. The Russian Federation demonstrates a gradual increase in the number of blood serum samples with antibodies to A/H9N2 virus.