PHWR Public Health Weekly Report

Objectives: The present report summarizes the key measures and outcomes implemented by the Korea Disease Control and Prevention Agency (KDCA) during the 2024–2025 season (October 1, 2024–September 11, 2025) to prevent human infection with avian influenza (AI). It also provides evidence for future preparedness and responses to emerging influenza.
Methods: AI human infection, a Category I National Notifiable Infectious Disease, is mainly transmitted through contact with infected animals or contaminated environments. The KDCA operated a Central AI Human Infection Response Task Force, supported local governments, and strengthened One Health collaboration with the MAFRA (Ministry of Agriculture, Food and Rural Affairs) and the MCEE (Ministry of Climate, Energy and Environment). Primary actions encompassed seasonal influenza vaccination for AI responders; updated guidelines; three joint ministerial meetings; reinforced hotline operations, newly established joint field training; and training programs for AI responders.
Results: During the 2024–2025 season, 52 cases of highly pathogenic AI were reported in poultry, 43 cases in wild birds, and 1 case in a wild mammal (leopard cat). A total of 7,790 high-risk individuals were placed under a 10-day active surveillance. All suspected cases tested negative, and no human infections were confirmed. Detection of AI in a wild mammal, along with the persistent global risk, prompted the KDCA to expand its task force to a year-round system in 2025 and strengthen inter-ministerial collaboration.
Conclusions: Relative to previous season, highly pathogenic avian influenza cases increased from 51 to 96, and the number of high-risk contacts rose markedly from 3,986 to 7,790 cases; however, the 2024–2025 season concluded with no confirmed human case. The KDCA will continue One Health–based preparedness to prevent human AI infection.

Objectives: This study quantitatively evaluated the levels of natural and mechanical ventilation in nursing homes and group homes in Seosan, the Republic of Korea, and estimated the airborne transmission risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Delta variant) according to ventilation conditions, with the aim of emphasizing the need for improved ventilation in infection-vulnerable facilities.
Methods: On-site investigations were conducted in 23 nursing homes and four group homes. Bedroom ventilation rates were directly measured, and air changes per hour (ACH) were calculated by using supply and exhaust airflow data and room volume. The Korea Disease Control and Prevention Agency airborne transmission risk assessment tool was also applied to estimate infection risk under a scenario involving one infectious SARS-CoV-2 Delta variant case and a 3-hour exposure period.
Results: The average frequency of natural ventilation was 5.5±2.3 events per day, with a mean duration of 15.4±10.4 minutes per event. The mean total ventilation rate in bedrooms was 1.4±0.9 ACH. Only 11.1% of the facilities achieved ≥2 ACH through natural ventilation alone, while none achieved ≥2 ACH through mechanical ventilation alone. In the 19 facilities equipped with mechanical ventilation systems, combined operation with natural ventilation reduced the estimated infection risk by an average of 11.4±6.9%p relative to natural ventilation alone (95% confidence interval: 7.9–14.7).
Conclusions: Reliance on natural ventilation alone is insufficient for mitigating airborne infection risk. Thus, enhanced design and operation of mechanical ventilation systems, together with the adoption of ACH-based standards and mandatory mechanical ventilation requirements, should be incorporated into evaluation criteria for long-term care facilities.