Abstract
This study investigated the long-term trends in human parainfluenza virus (HPIV) types 1, 2, and 3 in Korea by year, age group, and season. A total of 23,284 nasopharyngeal swabs collected from patients with respiratory symptoms at a tertiary hospital in Korea between 2007 and 2024 were tested for HPIV using real-time reverse-transcription polymerase chain reaction. Of the 23,284 specimens tested, 481 were positive for HPIV-1, 164 for HPIV-2, and 1102 for HPIV-3. HPIV-3 showed the highest incidence between 2010 and 2016, a decline after 2018, a sharp decline during the 2020 COVID-19 pandemic, and a resurgence in 2021. HPIV-1 and HPIV-2 incidence fluctuated between 2007 and 2019, followed by a sharp decline in 2020. HPIV-3 activity peaked in spring and summer, whereas HPIV-1 and HPIV-2 peaked in autumn. For all three types, infection rates were generally highest among children aged 1-12 years, followed by those in infants, but infection rates varied significantly by type, year, season, and age group. These findings emphasize targeted pediatric prevention, predictive modeling of seasonal peaks, and continued molecular surveillance to clarify the genetic and antigenic diversity of HPIV types after the pandemic, supporting the Sustainable Development Goals (SDG 3 for Good Health and Well-Being).