[The Republic of Korea 2023-2024 Influenza and Respiratory Viruses Laboratory Surveillance Report]

The study aim was to examine the detection patterns of respiratory virus circulation in the Republic of Korea from week 36 of 2023 to week 35 of 2024, with a focus on characterizing influenza viruses. The purpose of this study was to support the selection of vaccine strains and strengthen public health preparedness.

Respiratory specimens were collected from 18,040 symptomatic individuals using a national sentinel surveillance network. Real-time reverse transcription polymerase chain reaction testing was performed to identify the causative respiratory pathogens. For influenza viruses, further analyses were performed to assess genetic similarity with the vaccine strains, antigenic characteristics, and antiviral resistance.

Influenza viruses were detected in 15.1% of specimens, with the following subtype distributions: A(H1N1)pdm09 (41.7%), A(H3N2) (29.3%), and B type (29.1%). The genetic analysis showed that the circulating strains belonged to phylogenetic groups similar to the current vaccine strains. Further, no mutations associated with resistance to antiviral drugs (Oseltamivir, Zanamivir, and Peramivir, Baloxavir) were identified. The antigenic analysis confirmed effective neutralizing activity against the vaccine strains. Among respiratory viruses, severe acute respiratory syndrome coronavirus 2 was the most frequently detected (15.1%), followed by rhinovirus (14.9%), adenovirus (9.9%), parainfluenza virus (5.6%), respiratory syncytial virus (5.0%), human metapneumovirus (4.2%), human coronavirus (3.8%), and bocavirus (3.2%).

The continuous surveillance of influenza and respiratory virus trends is essential to inform vaccine strain selection and enhance public health response strategies. Our division will conduct continuous surveillance of the epidemiological trends of respiratory viruses, including influenza, and ensure the timely provision of data for public health interventions.