Epidemiologic and Seasonal Trends of Four Endemic Human Coronaviruses in Korea from 2018 to 2024.

BACKGROUND: Human coronaviruses (HCoVs) 229E, NL63, OC43, and HKU1 are globally endemic causes of respiratory tract infections. However, long-term epidemiological data from Korea, particularly after the emergence of COVID-19, remain limited. METHODS: We retrospectively analyzed multiplex real-time reverse transcription PCR (RT-PCR) results for respiratory viruses obtained at a single university hospital between November 2018 and April 2024. The epidemiological patterns of the four common HCoVs were evaluated according to age group and seasonality. RESULTS: Among 6,914 respiratory samples, HCoVs were detected in 184 patients (101 adults and 83 children). HCoV-OC43 was the most frequently identified subtype in both adults (34.7%) and children (49.4%). Pediatric cases peaked in November-December, whereas adult cases peaked in December-January. A resurgence of HCoV circulation was observed in November 2023, following the COVID-19 pandemic. CONCLUSIONS: Endemic HCoVs continue to circulate in Korea with distinct seasonal and age-related patterns. The reemergence of HCoVs after the COVID-19 pandemic highlights the need for accurate nationwide surveillance and analysis in relation to endemic SARS-CoV-2 to guide respiratory disease management.