Circulation and characterization of seasonal influenza viruses in Southern Vietnam, 2018 – 2020

Abstract

Through surveillance systems such as influenza-like illness (ILI) surveillance, severe acute respiratory infection (SARI) surveillance, and severe viral pneumonia (SVP) surveillance, 3497 cases were enrolled with the objective to describe the circulation and characteristics of seasonal influenza viruses in the South of Vietnam in the period of 2018 - 2020. In which, the total number of positive cases of seasonal influenza viruses are 711 cases (accounting for
711/3497 – 20,3%). The number of positive cases for influenza A/H1pdm09, A/H3 and influenza B were 381 – 10,9%; 148 – 4,2% and 182 – 5,2%, respectively. Genetically, influenza A/H1pdm09 strains belong to clade 6B.1A, influenza A/H3 strains belong to clade 3C.2a1b and influenza B strains mostly belong to the Victoria lineage clade V1A. In 2018, there was a case of influenza B belonging to the Yamagata lineage clade Y3. All the surveillance systems have provided much of epidemiological and virological information
needed to develop technical guidance, and guide actions to prevent influenza viruses and other respiratory viruses.