PHWR Public Health Weekly Report

Objectives: This study characterizes the detection patterns of respiratory viruses and the virological characteristics of influenza viruses in the Republic of Korea from week 36 of 2024 to week 35 of 2025, thereby contributing to evidence-based infection control policies and strengthening public health responses.
Methods: Respiratory specimens were collected from patients with influenza-like illness at sentinel medical institutions and tested at 18 regional Institutes of Health and Environment. Molecular assays were conducted to detect respiratory viruses, and the distribution of etiologic agents was subsequently analyzed. The influenza viruses were further characterized through genetic, antigenic, and antiviral-resistance analyses to assess their similarity to the vaccine strains and susceptibility to antiviral agents.
Results: Among specimens collected during the 2024–2025 season, influenza virus was the most frequently detected respiratory virus (15.2%), followed by rhinovirus (15.0%), severe acute respiratory syndrome coronavirus 2 (9.7%), parainfluenza virus (6.2%), adenovirus (4.9%), human metapneumovirus (4.8%), human coronavirus (4.7%), respiratory syncytial virus (3.6%), and human bocavirus (3.2%). The influenza virus subtypes included A(H1N1)pdm09 (39.6%), influenza B virus (36.8%), and A(H3N2) (23.6%). Circulating influenza viruses were genetically and antigenically similar to the 2024–2025 seasonal vaccine strains, and no antiviral-resistance mutations were detected.
Conclusions: The epidemiology of influenza and other respiratory viruses varies across seasons, underscoring the importance of continuous surveillance to inform infection control policies and strengthen public health preparedness. Through the Korea Respiratory Virus Integrated Surveillance System, our division will continue to monitor the circulation of respiratory viruses and the characteristics of influenza viruses and disseminate these findings on an ongoing basis.

Objectives: The Korea Respiratory Virus Integrated Surveillance System (K-RISS) operates as a sentinel surveillance system. This study complements K-RISS by testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients who presented to healthcare facilities with respiratory symptoms but were not tested for coronavirus disease 2019 (COVID-19).
Methods: Among specimens collected from patients presenting to healthcare facilities with respiratory symptoms and submitted for multiplex testing for 19 respiratory viruses, specimens that tested negative for all respiratory viruses were additionally tested for SARS-CoV-2 using molecular assays. Whole-genome sequencing using next-generation sequencing was performed on SARS-CoV-2–positive specimens to characterize circulating sublineages.
Results: Of the 5,400 total specimens, 591 were SARS-CoV-2–positive, resulting in an overall positivity rate of 10.9%. This positivity rate exhibited a seasonal pattern: it increased after July, peaked in August, and subsequently declined. This trend aligned with the annual SARS-CoV-2 detection rates observed by K-RISS. Moreover, changes in variant prevalence identified through whole-genome sequencing were comparable to those reported by K-RISS.
Conclusions: This study’s approach of testing and analyzing respiratory virus-negative specimens after Korea transitioned to the current sentinel surveillance system identified additional SARS-CoV-2–positive specimens. This enabled a reliable assessment of domestic COVID-19 transmission and variant circulation occurring during the surveillance transition period. It also confirmed that the current K-RISS delivers representative insights into community-level epidemic trends.

Objectives: The Korea Disease Control and Prevention Agency has conducted a mobile tuberculosis (TB) screening program for vulnerable populations since 2020. This operation includes homeless individuals with limited access to healthcare and who are living on streets, in facilities, or in jjokbang areas. This study analyzes the program’s outcomes and provides recommendations for future implementation.
Methods: Participants were screened at their residences to increase accessibility. The screening procedure includes a prescreening questionnaire, chest X-ray, and sputum testing. Individuals with TB-related symptoms or abnormal chest X-ray findings must undergo sputum testing. This study used the chi-square test with statistical significance set at 0.05 to analyze differences in TB detection rates across participant characteristics.
Results: A total of 31,596 individuals were screened between 2023 and 2024, and 36 TB cases were identified (113.9 per 100,000 screenings). Male sex (p=0.012), poor housing conditions (p=0.001), medically vulnerable status (p=0.030), TB-related symptoms (p=0.020), a history of TB (p=0.001), and abnormal chest X-ray findings (p≤0.001) were significantly associated with TB detection in 2023. Poor housing conditions (p=0.009) and abnormal chest X-ray findings (p≤0.001) remained significant in 2024. Approximately 75.0% of the detected cases were classified as inactive TB on chest X-ray, and most individuals were asymptomatic or had displayed mild symptoms.
Conclusions: The mobile TB screening program facilitates early detection by identifying cases that may not be discernible through symptom-based screening alone. Strengthening mobile screening and periodic follow-up for vulnerable populations may further improve early detection and treatment outcomes.