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Objectives: To describe and evaluate epidemiological investigation results and containment measures implemented in Busan, where 108 cases were confirmed with coronavirus disease 2019 (COVID-19) between February 21, 2020 and March 24, 2020.Methods: Any individual who tested positive for COVID-19 was classified as a confirmed case. Measures were taken to identify the source of infection and trace and quarantine contacts. Serial intervals were estimated and the effective reproduction number was computed.Results: Of the total 18,303 COVID-19 tests performed between January 16, 2020 and March 24, 2020 in Busan, 108 yielded positive results (positive test rate, 0.6%). All confirmed cases were placed in isolation at hospitals. Of the 108 confirmed cases, 59 (54.6%) were female. The most common age group was 20-29 years with 37 cases (34.3%). Regarding symptoms at the time of diagnosis, cough (n=38, 35.2%) and fever (n=34, 31.5%) were most common; 12 cases (11.1%) were asymptomatic. The source of infection was identified in 99 cases (91.7%). A total of 3,223 contacts were identified and quarantined. Household contacts accounted for 196, and the household secondary attack rate was 8.2% (95% confidence interval [CI], 4.7 to 12.9). The mean serial interval was estimated to be 5.54 days (95% CI, 4.08 to 7.01). After February 26, (Rt) remained below 1 in Busan.Conclusions: The early containment strategy implemented in Busan shows that control is possible if outbreaks are of limited scope. In preparation for future outbreaks, public health and healthcare systems should be re-examined and put in a ready state. [ABSTRACT FROM AUTHOR]

Objectives: In September 2023, an outbreak of food-borne disease occurred among students on a training ship docked in Busan. This was an epidemiological investigation with the aim of improving infection prevention activities and group meal service practices on board ships., Methods: In this study, a case was defined as an individual who experienced diarrhea more than twice a day during their training period aboard the training ship. A total of 171 exposed individuals including 6 food handlers was well-defined; therefore, a retrospective cohort study was conducted. We administered a questionnaire and conducted laboratory tests including 38 rectal swab samples. Relative risk (95% confidence interval) for each food item was calculated., Results: Of the 165 students and school staff members, 41 met the case definition, resulting in an attack rate of 24.8%; all cases were students. The shape of the epidemic curve was unimodal, with the peak from 0:00 to 06:00 on September 7, 2023. Clostridium perfringens was detected in 9 cases, and no other pathogens were found. Significant relative risk was shown in 11 different food items., Conclusion: Clostridium perfringens was the causative pathogen of this outbreak on the training ship. Due to the lack of preserved food samples, the exact source of infection could not be confirmed. Ships are not classified as collective dining facilities, leaving them in a management blind spot. Therefore, specialized guidelines, voluntary inspections by the operating entities, and continuous education for managers and staff are necessary.

Background: This study aimed to investigate differences in the anti-hepatitis A virus (HAV) antibody seropositivity rate by age and gender., Methods: We collected information on anti-HAV immunoglobulin G and immunoglobulin M status from samples submitted for HAV antibody testing in 2012-2022. A total of 1,333,615 cases were included in the analysis., Results: By age, the seropositivity rate was represented by a U-shaped curve, such that the rate was low for the group aged 20 to 39 years and higher in those who were younger or older. Over time, the curve shifted rightward, and the seropositivity rate declined gradually in the group aged 35 to 39 years and older. A gender-based difference in antibody seropositivity rate was especially noticeable in the group aged 20 to 29 years. This difference between genders widened in the participants' early 20s-when men in the Republic of Korea enlist in the military-and the divergence continued subsequently for older individuals., Conclusion: These results indicate a higher risk of severe infection among older individuals and a gender-based difference in seroprevalence. Therefore, it is necessary to implement policies to promote vaccination in adults.

Objectives: To examine the effect of individual and area-level characteristics on the probability of public-private mix (PPM) support (PPM coverage) for tuberculosis (TB)., Methods: This study is a retrospective cohort design using TB reporting and treatment management data in Korea. We analyzed PPM coverage through multilevel logistic regression and empirical Bayesian estimation according to individual and area-level characteristics and their interaction., Results: Patients aged 0-29 years, women, of Korean nationality, treated at a general hospital, a one-time reporting, urban areas, and the lowest deprivation index (DI) showed higher PPM coverage. Due to the cross-level interaction, PPM coverage in the urban areas (slope=-0.048, p<0.001) had a higher level but a steeper negative deprivation gradient than in rural areas (slope= -0.015, p<0.001). For a general hospital, the PPM coverage in urban is high but more significantly decreased than in rural areas with the higher DI (urban: slope=-0.047, p<0.001; rural: slope=-0.031, p<0.001). For clinics and hospitals, the effect of DI did not appear in urban areas, but in rural areas, the higher the DI, the higher the PPM coverage with a slope of 0.046 (p<0.001) and 0.063 (p<0.001), respectively., Conclusions: The PPM program created a significant disparity in PPM coverage between urban-rural areas and type of healthcare provider according to DI. Considering the high risk of TB incidence in areas with higher DI, institutional improvement and program redesign are needed to improve accessibility and equity.

Objectives: In July 2019, there were multiple reports on patients with hepatitis A among the visitors of a restaurant in Busan. The current study presents the results of an epidemiological investigation and outlines the supplementary measures that would help with hepatitis A control., Methods: A cohort study was conducted for all 2,865 customers who visited restaurant A from June to July. Using a standardized questionnaire, participants reported the presence of hepatitis A symptoms and whether they had consumed any of 19 food items. As for participants who had visited public health centers, their specimens were collected., Results: From the study cohort, 155 participants (5.4%) had confirmed hepatitis A. The epidemic curve was unimodal, and the median number of days from the restaurant visit to symptom onset was 31 days. A genotype analysis indicated that 89 of 90 tested patients had hepatitis A virus (HAV) genotype 1A. The results of a multivariate logistic regression analysis indicated that the ingestion of salted clams increased the risk of hepatitis A by 68.12 times (95% confidence interval [CI], 9.22 to 510.87). In an unopened package of salted clams found and secured through traceback investigation, HAV genotype 1A was detected., Conclusions: To prevent people from ingesting uncooked clams, there needs to be more efforts to publicize the dangers of uncooked clams; the food sampling test standards for salted clams should also be expanded. Furthermore, a laboratory surveillance system based on molecular genetics should be established to detect outbreaks earlier.

This paper studies a stochastic vector-host epidemic model with direct transmission in random environment, governed by a system of stochastic differential equations with regime-switching diffusion. We first examine the existence and uniqueness of a positive global solution. Then, we investigate stability properties of the solution, including almost sure and pth moment exponential stability and stochastic asymptotic stability. Moreover, we study conditions for the existence and uniqueness of a stationary distribution. Numerical simulations are presented to illustrate the theoretical results.

This is a retrospective cohort study using notification data in South Korea. We evaluated the nationwide status, regional differences, and the determinants of treatment outcomes among tuberculosis patients. Treatment success rate improved from 77.0% in 2012 to 86.0% in 2015. The lost to follow-up rate was higher among older people, males, and foreign nationals. Health care facilities designated for the Public-Private Mix (PPM) project showed higher success rate and lower rate of lost to follow-up. Moreover, municipalities with low regional deprivation index had higher PPM project coverage. Since there is a large regional difference in the coverage of the PPM project, an additional community-based support program should be implemented, especially for tuberculosis patients residing in region with low PPM project coverage.