Fungal Endophthalmitis Outbreak after Cataract Surgery, South Korea, 2020.

In November 2020, an unusual increase in fungal endophthalmitis cases after cataract surgery was reported to the Korea Disease Control and Prevention Agency, South Korea. We initiated an outbreak investigation to identify the cause. We identified 156 cases nationwide, 62 confirmed and 94 probable. Most case-patients were exposed during surgery to ocular viscoelastic devices (OVDs) from the same manufacturer (company A). We isolated Fusarium spp. from 50 confirmed cases. Molecular identification of 39 fungal isolates from clinical samples and 13 isolates from OVDs confirmed F. oxysporum caused the infections. The risk ratio for fungal endophthalmitis from company A's OVDs was 86.0 (95% CI 27.4-256.9), much higher than risk from other manufacturers' products. We determined this fungal endophthalmitis outbreak was caused by a contaminated lot of OVDs and recommended discontinued use of this product. Early recognition of outbreaks and joint responses from related government agencies can reduce risk for fungal endophthalmitis.

Serial Intervals and Household Transmission of SARS-CoV-2 Omicron Variant, South Korea, 2021.

To clarify transmissibility of the severe acute respiratory syndrome coronavirus 2 Omicron variant, we determined serial intervals and secondary attack rates among household contacts in South Korea. Mean serial interval for 12 transmission pairs was 2.9 days, and secondary attack rate among 25 households was 50.0%, raising concern about a rapid surge in cases.

Time from Exposure to Diagnosis among Quarantined Close Contacts of SARS-CoV-2 Omicron Variant Index Case-Patients, South Korea.

To determine optimal quarantine duration, we evaluated time from exposure to diagnosis for 107 close contacts of severe acute respiratory syndrome coronavirus 2 Omicron variant case-patients. Average time from exposure to diagnosis was 3.7 days; 70% of diagnoses were made on day 5 and 99.1% by day 10, suggesting 10-day quarantine.

Community Transmission of SARS-CoV-2 Omicron Variant, South Korea, 2021.

In South Korea, a November 2021 outbreak caused by severe acute respiratory syndrome coronavirus 2 Omicron variant originated from 1 person with an imported case and spread to households, kindergartens, workplaces, restaurants, and hospitals, resulting in 11 clusters within 3 weeks. An epidemiologic curve indicated rapid community transmission of the Omicron variant.

Importation and Transmission of SARS-CoV-2 B.1.1.529 (Omicron) Variant of Concern in Korea, November 2021.

In November 2021, 14 international travel-related severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.529 (omicron) variant of concern (VOC) patients were detected in South Korea. Epidemiologic investigation revealed community transmission of the omicron VOC. A total of 80 SARS-CoV-2 omicron VOC-positive patients were identified until December 10, 2021 and 66 of them reported no relation to the international travel. There may be more transmissions with this VOC in Korea than reported.

Epidemiological Characteristics of a COVID-19 Outbreak in a Psychiatric Hospital in Chung-buk.

This study investigated the causes and risks for infection spread in three psychiatric hospitals in Chung-buk, South Korea, to strategize measures to block transmission and prevent a large-scale epidemic. From December 2020 to January 2021, 358 inpatients of Psychiatric Hospitals A, B, and C were enrolled to identify the epidemiological characteristics of confirmed patients. Epidemic curves and propagation relationships were constructed and a genotype analysis was conducted. The index case inpatient from Hospital A transmitted the infection to patients in Hospitals B and C; the infection was confirmed in 47, 193, and 118 patients in Hospitals A, B, and C, respectively. The patient characteristics hampered communication and the close identification of symptom onset. The incidence rate was 10 (2.9%) among employees and 348 (35.8%) among inpatients. The relative risk was 12.1 (95% CI: 6.6-22.5) times higher among inpatients than employees. Next-generation sequencing confirmed the probable infection source as a genotype identical to that of two different outbreaks, although the infection spread was undetermined. Direct risk factors emerged from patient characteristics, wherein cohort isolation was meaningless due to uncontrolled communication. Indirect risk factors included hospital-specific problems due to external factors (non-patient system deficiencies or employee negligence). Prior inspections, a confirmation of non-infection, and institutional emergent measures are needed.

Analysis of pregnant women with critically severe COVID-19 in Republic of Korea from February 2020 and December 2021.

OBJECTIVES: This study aimed to describe the characteristics and risk factors for severe disease in pregnant women infected with coronavirus disease 2019 (COVID-19) from the early days of the COVID-19 epidemic in Korea to the predominant period of the Delta variant. METHODS: A retrospective cohort study was conducted among pregnant women diagnosed with COVID-19 between February 2020 and December 2021. Logistic regression analysis was performed to compare severe and mild cases after adjusting for pregnant women's age, nationality, infection route, outbreak area, infection period, symptoms, underlying disease, smoking status, trimester, and COVID-19 vaccination status. RESULTS: In total, 2,233 pregnant women were diagnosed with COVID-19 by December 2021. Among these, 96.7% had mild symptoms, 3.3% had severe symptoms, and 0.04% died. The risk factors for severe disease in pregnant women with confirmed COVID-19 were being in the age group of 35 to 45 years, having hyperlipidemia, being in the second or third trimester of pregnancy at the time of COVID-19 diagnosis, being infected during the Delta-predominant period, and having a fever (≥38 °C) at diagnosis. Furthermore, 47.1% of patients in the mild group and 84.9% of patients in the severe group had 3 or more risk factors. CONCLUSION: Pregnant women with COVID-19 mainly experienced mild symptoms, but those with risk factors were at a higher risk of developing severe symptoms. Therefore, treatment and follow-up management should be thoroughly implemented.

Evaluation of COVID-19 vaccine effectiveness in different high-risk facility types during a period of Delta variant dominance in the Republic of Korea: a cross-sectional study.

BACKGROUND: We evaluated the effectiveness of coronavirus disease 2019 vaccination in high-risk facilities in the Republic of Korea during the period when the highly transmissible Delta variant was prevalent. Additionally, we aimed to explore any disparities in vaccine effectiveness (VE) across various types of institutions, specifically distinguishing between non-medical and medical establishments. METHODS: We examined 8 outbreak clusters covering 243 cases and 895 contacts from 8 high-risk facilities divided into 2 groups: group A (4 non-medical institutions) and group B (4 medical institutions). These clusters were observed from July 27, 2021 to October 16, 2021 for the attack rate (AR) and VE with respect to disease severity. A generalized linear model with a binomial distribution was used to determine the odds ratio (OR) for disease severity and death. RESULTS: AR was notably lower in group B (medical institutions). Furthermore, VE analysis revealed that group A exhibited higher effectivity for disease severity and death than group B. The OR for disease severity was 0.24 (95% confidence interval [CI], 0.03-2.16) for group A and 0.27 (95% CI, 0.12-0.64) for group B, with the OR for death at 0.12 (95% CI, 0.01-1.32) in group A and 0.34 (95% CI, 0.14-0.87) in group B. CONCLUSION: Although VE may vary across institutions, our findings underscore the importance of implementing vaccinations in high-risk facilities. Customized vaccination programs, tailored response plans, and competent management personnel are essential for effectively addressing and mitigating public health challenges.

Accuracy of Rapid Antigen Screening Tests for SARS-CoV-2 Infection at Correctional Facilities in Korea: March - May 2022.

BACKGROUND: The number of confirmed cases of individuals with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection increased rapidly due to the Omicron variant. Correctional facilities are vulnerable to infectious diseases, and they introduced rapid antigen tests (RATs) to allow for early detection and rapid response. We aimed to evaluate the diagnostic performance and usefulness of SARS-CoV-2 RATs in newly incarcerated people. MATERIALS AND METHODS: We conducted a cross-sectional study at correctional facilities in Korea from 9 March to 22 May 2022. The study population was newly incarcerated people who were divided into two groups. In one group, 799 paired SARS-CoV-2 RATs and real-time polymerase chain reaction (RT-PCR) were conducted simultaneously in 522 individuals in March 2022. In the other group, 4,034 paired RATs and RT-PCR consecutively in 4,034 participants; only individuals with negative RATs results underwent RT-PCR from April to May 2022. We analyzed data using descriptive statistics and a logistic regression model. RESULTS: Among the 799 specimens in March, RT-PCR was positive in 72 (9.0%), and among the 4,034 specimens in April - May 2022, RT-PCR was positive in 40 (1.0%). Overall, the RATs had a sensitivity of 58.3%, specificity of 100.0%, positive predictive value (PPV) of 100.0%, and negative predictive value (NPV) of 96.0%. Asymptomatic individuals constituted 98.2% of the study group, and symptomatic individuals 1.8%. In asymptomatic cases, the sensitivity of RATs was 52.5%, specificity was 100.0%, PPV was 100.0%, and NPV was 96.3%. In symptomatic cases, the sensitivity of RATs was 84.6%, specificity was 100.0%, PPV was 100.0%, and NPV was 33.3%. Sensitivity (P = 0.034) and NPV (P = 0.004) differed significantly according to the presence and absence of symptoms, and the F1 score was the highest at 0.9 in symptomatic individuals in March. There was a positive linear trend in the proportion of false-negative RATs in newly incarcerated people following the weekly incidence of SARS-CoV-2 (P = 0.033). The best-associated predictors of RATs for SARS-CoV-2 infection involved symptoms, timing of sample collection, and repeat testing. CONCLUSION: Sensitivity and NPV significantly depend on whether symptoms are present, and the percentage of false negatives is correlated with the incidence. Thus, using RATs should be adjusted according to the presence or absence of symptoms and the incidence of SARS-CoV-2 infection in the community. RATs could be a useful screening tool as an effective first-line countermeasure because they can rapidly identify infectious patients and minimize SARS-CoV-2 transmission in correctional facilities.

The effectiveness of Paxlovid treatment in long-term care facilities in South Korea during the outbreak of the Omicron variant of SARS-CoV-2.

OBJECTIVES: On November 5, 2021, Pfizer Inc. announced Paxlovid (nirmatrelvir +ritonavir) asa treatment method that could reduce the risk of hospitalization or death for patients withconfirmed coronavirus disease 2019 (COVID-19). METHODS: From February 6, 2022 to April 2, 2022, the incidence of COVID-19 and the effectsof treatment with Paxlovid were analyzed in 2,241 patients and workers at 5 long-term carefacilities during the outbreak of the Omicron variant of severe acute respiratory syndromecoronavirus 2 in South Korea. RESULTS: The rate of severe illness or death in the group given Paxlovid was 51% lower thanthat of the non-Paxlovid group (adjusted risk ratio [aRR], 0.49; 95% confidence interval [CI],0.24-0.98). Compared to unvaccinated patients, patients who had completed 3 doses of thevaccine had a 71% reduced rate of severe illness or death (aRR, 0.29; 95% CI, 0.13-0.64) and a65% reduced death rate (aRR, 0.35; 95% CI, 0.15-0.79). CONCLUSION: Patients given Paxlovid showed a lower rate of severe illness or death and alower fatality rate than those who did not receive Paxlovid. Patients who received 3 dosesof the vaccine had a lower rate of severe illness or death and a lower fatality rate than theunvaccinated group.

An outbreak of SARS-CoV-2 reinfection in a long-term care facility in South Korea.

We report a cluster of 12 cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection in a long-term care facility in South Korea. There were two outbreaks of SARS-CoV-2 infection in the facility at the beginning and end of October 2021, respectively. All residents in the facility were screened for SARS-CoV-2 infection using RT-PCR as part of the investigation of the second outbreak. Twelve residents, who had infection confirmed during the first outbreak, were found to be re-positive for RT-PCR test at the second outbreak. 8 Of 12 RT-PCR re-positive cases were confirmed as reinfections based on investigation through the whole genome sequencing, viral culture, and serological analysis, despite of the short interval between the first and second outbreaks (29-33 days) and a history of full vaccination for 7 of the 12 re-positive cases. This study suggests that decreased immunity and underlying health condition in older adults makes them susceptible to reinfection, highlighting the importance of prevention and control measures regardless of vaccination status in long-term care settings.