Ae Kyung Park, Ph.D., Il-Hwan Kim, Ph.D., Chae Young Lee, B.S., Jeong-Ah Kim, Ph.D., Hyeokjin Lee, M.S., Heui Man Kim, Ph.D., Nam-Joo Lee, M.S., SangHee Woo, M.S., Jaehee Lee, B.S., JeeEun Rhee, Ph.D., Cheon-Kwon Yoo, Ph.D., and Eun-Jin Kim, Ph.D.. Ann Lab Med 2023;43:211-3. https://doi.org/10.3343/alm.2023.43.2.211

Background/Objectives: Pertussis continues to pose a substantial global health challenge despite widespread vaccination programs. This study aimed to analyze the epidemiological characteristics of recent pertussis cases in the Gyeongnam region of South Korea. Methods: We analyzed 419 pertussis cases in the Gyeongnam region of South Korea between October 2023 and April 2024, using data collected from epidemiological investigation reports, medical records, and interviews with health officials and school staff. Results: Our analysis revealed a distinct age distribution pattern with minimal cases in infants (0.2% under 1 year) and young children (7.9% in ages 1–6 years), while school-aged children showed the highest incidence (31.8% in ages 7–9 years, 36.0% in ages 10–12 years). The outbreak pattern demonstrated a progressive shift from preschool and elementary school students to middle and high school students. The time from symptoms onset to diagnosis varied significantly across age groups, with a median of 3.0 days (1.0–6.0) overall; notably, this was longer in high school students at 5.0 days (2.3–8.0) (p = 0.023). While 92.4% (365/395) of cases were fully vaccinated, substantial delays were observed in third and fourth dose administration (18.2% and 25.8%, respectively), with considerable timing variability for the fifth and sixth doses. Conclusions: Our findings highlight the changing epidemiology of pertussis in South Korea, characterized by an age shift toward older children. These results emphasize the need for enhanced surveillance focusing on school-aged populations and the reassessment of vaccination strategies, particularly regarding booster dose timings and adherence.

This study investigated the infectivity of severe acute respiratory syndrome (SARS-CoV-2) in individuals who re-tested positive for SARS-CoV-2 RNA after recovering from their primary illness. We investigated 295 individuals with re-positive SARS-CoV-2 polymerase chain reaction (PCR) test results and 836 of their close contacts. We attempted virus isolation in individuals with re-positive SARS-CoV-2 PCR test results using cell culture and confirmed the presence of neutralizing antibodies using serological tests. Viral culture was negative in all 108 individuals with re-positive SARS-CoV-2 PCR test results in whom viral culture was performed. Three new cases of SARS-CoV-2 infection were identified among household contacts using PCR. Two of the three new cases had had contact with the index patient during their primary illness, and all three had antibody evidence of past infection. Thus, there was no laboratory evidence of viral shedding and no epidemiological evidence of transmission among individuals with re-positive SARS-CoV-2 PCR test results.

Objectives: Coronavirus disease 2019 (COVID-19) has been declared a global pandemic owing to the rapid spread of the causative agent, severe acute respiratory syndrome coronavirus 2. Its Delta and Omicron variants are more transmissible and pathogenic than other variants. Some debates have emerged on the mechanism of variants of concern. In the COVID-19 wave that began in December 2021, the Omicron variant, first reported in South Africa, became identifiable in most cases globally. The aim of this study was to provide data to inform effective responses to the transmission of the Omicron variant.Methods: The Delta variant and the spike protein D614G mutant were compared with the Omicron variant. Viral loads from 5 days after symptom onset were compared using epidemiological data collected at the time of diagnosis.Results: The Omicron variant exhibited a higher viral load than other variants, resulting in greater transmissibility within 5 days of symptom onset.Conclusion: Future research should focus on vaccine efficacy against the Omicron variant and compare trends in disease severity associated with its high viral load.

Objectives: Scrub typhus, an acute disease caused by Orientia tsutsugamushi and transmitted by larval chigger mites, is a representative autumn febrile illness in the Republic of Korea. We examined epidemiological characteristics underlying spatial heterogeneity in Busan Metropolitan City to inform region-specific prevention and control policies.Methods: We analyzed 1,645 confirmed and suspected scrub typhus cases reported in Busan from 2019 to 2023. Crude incidence rates and age-standardized incidence rates (ASIRs) per 100,000 population were calculated using the 2021 mid-year population. The chi-square test assessed associations between disease occurrence and exposure activities within the preceding 30 days. Correlation analyses examined the relationships of ASIR with environmental indicators, including per capita urban forest area, and epidemiological indicators, including prior infectious disease education.Results: The overall mean ASIR in Busan was 8.35 per 100,000 population, below the national average. However, incidence was higher in peri-urban districts, including Gijang-gun (26.12/100,000) and Gangseo-gu (15.02/100,000), than in central urban districts such as Jung-gu (2.20/100,000). Higher incidence was observed among women and older adults (≥60 years). ASIR correlated strongly with per capita urban forest area (r=0.92; 95% confidence interval, 0.79–0.97; p<0.001). Regional differences were significant for agriculture/forestry, gardening, and general outdoor activities (p<0.001). Districts with higher incidence also displayed higher rates of infectious disease education, although this may reflect reverse causation.Conclusion: In Busan, scrub typhus incidence was concentrated in peri-urban districts. These findings support region-specific prevention strategies, evaluation of infectious disease education, enhanced mite surveillance, and practical protective measures during fieldwork.

항공기가 이·착륙시 구름대를 지나며 빙점 이하의 온도에서 비행할 때 액적이 항공기와 충돌하면서 날개, 동체 등에 결빙이 발생한다. 본 연구에서는 결빙 다중 익형의 공력 및 소음 특성에 관한 연구를 수행하였다. Lattice-Boltzmann Method(LBM)를 이용하여 공력해석을 수행하였고, 공력해석 결과를 바탕으로 투과면 기법을 적용한 Ffowcs Williams-Hawkings 음향 상사법을 이용하여 공력소음을 예측하였다. 실험데이터가 존재하는 받음각 5.5° 조건에서 결빙이 없는 다중 익형에 대한 공력성능 및 유동장 비교를 통해 해석자에 대한 검증을 수행하였다. 받음각 변화에 따라 결빙 형성이 다중 익형의 공력 및 소음 발생 특성에 미치는 영향을 분석하기 위해 이·착륙 각도인 받음각 8°와 실속 부근 각도인 17° 조건에서 결빙 다중익형에 대한 전산공력소음 해석을 수행하였다. 결빙 형상에 의해 발생하는 박리 유동과 재순환 유동을 분석하였고, 특히 받음각 17° 조건에서 Slat Cove 근처에서 발달하는 Cavity Flow의 영향이 감소함에 따라 소음이 감소하는 것을 확인하였다.