We investigated respiratory virus epidemiology in older adults across pre-pandemic (2007–2019), pandemic (2020–2022), and post-pandemic (2023–2024) periods, focusing on how public health interventions shaped surveillance, prevalence, and sex-specific trends. We conducted a retrospective cross-sectional study at a 1000-bed tertiary hospital in the Republic of Korea during 2007–2024, analyzing 4692 nasopharyngeal swab specimens collected from adults aged ≥ 65 years with suspected respiratory infections during 2007–2024. The specimens were tested for 15 respiratory viruses using multiplex real-time polymerase chain reaction. The outcomes included virus-specific detection rates and seasonal, sex-based and temporal trends before and after the COVID-19 pandemic. During the pre-pandemic period, older adults accounted for 13.2% of the tested individuals, which significantly increased to 52.0% in the later periods. Influenza A was the most frequently detected virus, followed by rhinovirus and human metapneumovirus. Influenza, RSV A/B, and coronaviruses 229E and OC43 showed peak positivity in winter, parainfluenza virus type 3 peaked in summer, and rhinovirus circulated year-round. Virus circulation was markedly suppressed during 2020–2022 and partially rebounded during 2023–2024. This study highlights the shift in diagnostic access and epidemiologic patterns of respiratory virus infections in older adults following the COVID-19 pandemic.

Background/Objectives: Respiratory syncytial virus A (RSV A) is the leading cause of respiratory infections, particularly in vulnerable populations. This study aimed to investigate the long-term epidemiological trends of RSV A infection in the Republic of Korea over an 18-year period (2007–2024), with emphasis on age, sex, and seasonal differences. Methods: A total of 23,284 nasopharyngeal swab specimens were analyzed by multiplex real-time PCR. Statistical comparisons were performed using the chi-square test. Results: The RSV A-positivity rate was highest in 2007 (19.7%) and lowest in 2021 (0.1%) (p < 0.001). Infants (0 years) exhibited the highest infection rate (18.5%, 95% CI: 17.3–19.6), whereas adults aged 20–64 years and older adults showed significantly lower rates (0.7% and 0.9%, respectively). Seasonal peaks occurred in winter (15.3%) and autumn (14.7%), indicating earlier onset of RSV A circulation. No significant difference was found between sexes (p = 0.196). Conclusions: This study provides the first long-term retrospective analysis of RSV A trends in the Republic of Korea and reveals a shift toward an earlier seasonal onset. These findings support the need for earlier preventive strategies and optimized vaccination timing, particularly for high-risk groups, such as infants. These findings underscore the importance of seasonal variation and the potential influence of environmental factors, such as ambient temperature, relative humidity, and geographic latitude, on RSV A transmission patterns in Korea, although these variables were not directly analyzed in the present study and warrant further investigation.

HSV-1 is associated with oral lesions and non-sexual transmission; HSV-2 is primarily transmitted through sexual contact and causes genital infections. Understanding the epidemiological dynamics of both viruses is essential for guiding targeted public-health responses. We conducted a retrospective analysis of 177,599 clinical specimens collected between September 2018 and December 2022 from patients with symptoms suggestive of sexually transmitted infections (STIs) at healthcare institutions across South Korea. HSV-1 and HSV-2 were identified using a real-time PCR assay; positivity rates were stratified by age, sex, specimen type, and year of testing. The overall positivity rate was 0.26% for HSV-1 and 1.60% for HSV-2. HSV-1 was most prevalent among individuals aged <19 years; HSV-2 showed the highest positivity in females aged 20–29 years, declining with age thereafter. HSV-2 positivity was significantly higher in females than in males. A significant decline in HSV-2 positivity was observed over the 5-year study period, while HSV-1 positivity remained stable. This nationwide PCR-based study reveals distinct age- and sex-related epidemiological patterns of HSV-1 and HSV-2. The findings support the need for age-specific and gender-specific STI screening strategies and health education programs. The declining trend in HSV-2 infection may reflect the impact of recent public-health initiatives.

Human adenoviruses (HAdVs; genus Mastadenovirus, family Adenoviridae) are major etiologic agents of respiratory infections, exerting a disproportionately large impact on children. However, no long-term study to date has spanned pre- and post-pandemic periods in a Korean tertiary setting. Here, we retrospectively analyzed 23,284 nasopharyngeal swabs collected between 2007 and 2024 at a tertiary medical center in South Korea. Most specimens were obtained from inpatients and outpatients presenting with fever or respiratory symptoms for differential viral diagnosis. HAdV was detected using real-time PCR, and positivity rates were compared by year, season, and age group. Overall, 2043 tested positive for HAdV. Annual positivity peaked in 2010, 2013, and 2016, followed by a sharp decline during the coronavirus disease 2019 pandemic, reaching its lowest level in 2024. Positivity was higher in summer and spring than in winter. Children aged 1–5 years had the highest positivity, whereas adults and older adults showed markedly lower rates. The disproportionate burden among children underscores the need for targeted surveillance, school-based infection control, and region-specific preparedness strategies. These findings provide crucial long-term evidence into adenovirus circulation in the post-pandemic era and provides an evidence-based foundation for future public health policy and infection control planning.

We aimed to characterize age-stratified C-reactive protein (CRP) patterns across respiratory virus infections, assess age-related CRP shifts in virus-not-detected-by-PCR episodes, and evaluate the independent associations of age and virus type with CRP levels. We retrospectively analyzed 19,002 test-level episodes with paired respiratory PCR and serum CRP results from a single tertiary-care center between 2008 and 2024. Episodes were classified as virus-not-detected-by-PCR or virus-positive according to multiplex PCR results; the former was not considered a healthy control and may include off-panel infections, bacterial/mixed infections, false-negative results, or non-infectious inflammation. Descriptive analyses and multivariable linear regression of log-transformed CRP were used to assess adjusted associations. Median CRP increased with age in both virus-positive and virus-not-detected-by-PCR episodes, rising from 0.38 to 7.42 mg/dL across age groups in the latter. Age showed the strongest association with CRP. Adenovirus showed a positive adjusted association, whereas influenza A/B, respiratory syncytial virus A/B, and parainfluenza virus types 1 and 3 showed selective negative associations. Overall, CRP variation was more strongly associated with age-related clinical background than with virus type, although selective virus-associated differences were observed, supporting the interpretation of CRP as a non-specific, composite host-response indicator within broader clinical contexts.