In February 2012, an outbreak of gastroenteritis was reported in school A; a successive outbreak was reported at school B. A retrospective cohort study conducted in school A showed that seasoned green seaweed with radishes (relative risk 7·9, 95% confidence interval 1·1-56·2) was significantly associated with illness. Similarly, a case-control study of students at school B showed that cases were 5·1 (95% confidence interval 1·1-24·8) times more likely to have eaten seasoned green seaweed with pears. Multiple norovirus genotypes were detected in samples from students in schools A and B. Norovirus GII.6 isolated from schools A and B were phylogenetically indistinguishable. Green seaweed was supplied by company X, and norovirus GII.4 was isolated from samples of green seaweed. Green seaweed was assumed to be linked to these outbreaks. To our knowledge, this is the first reported norovirus outbreak associated with green seaweed.

Background This study aimed to estimate the effects of vaccine on reducing the mortality rate and the relationship between underlying diseases and death among long term care hospital residents during the Omicron epidemic. Methods This study included 2,507 inpatients at 18 long term care hospitals that experienced COVID-19 outbreaks more than twice in Daegu Metropolitan City and Gyeongsangbuk-do in Korea, from January 2022 to August 2022. Descriptive statistics were used to analyze participants’ demographic characteristics and mortality, which were expressed as percentages (%). Logistic regression analysis was performed to compare mortality, and the crude risk ratio (cRR) and adjusted risk risk (aRR) were estimated. The analysis model was adjusted for sex, age, region, history of Paxlovid priscription, vaccine status, reinfection, and presence, type, and number of underlying diseases. Results In terms of vaccination status, the aRR in the group with < 90 days after the 3 doses was 0.20 (CI:0.09–0.45) and ≥ 90 days was 0.14 (CI:0.06–0.32), that in the group with < 90 days after 4 doses was 0.18 (CI:0.06–0.43), compared with the non-vaccinated group. The fatality rate in the group prescribed Paxlovid was higher than that in the non-prescribed group. However, the difference was not statistically significant. The aRR of hypothyroidism was 5.75 (CI:1.10–30.13) and that of COPD and asthma were 2.84 (CI:1.15–6.99), compared with the group that did not have each underlying disease. Conclusion We confirmed the preventive effects of vaccination on death and the high risk of death from hypothyroidism, COPD, and asthma in COVID-19-confirmed patients in long term care hospitals.

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Objectives: The goal of this study was to help prevent and control the spread of coronavirus disease 2019 (COVID-19) by identifying transmission routes and risk factors in livestock slaughtering and processing facilities (SPFs) and establishing an optimal intervention strategy for outbreaks.Methods: This case series study was a demographic analysis of patients with confirmed COVID-19 associated with 5 SPFs in Korea between January and June 2021. Additionally, in a retrospective cohort study, the association between COVID-19 infection and risk factors was analyzed for SPFs at which outbreaks occurred.Results: The COVID-19 attack rates were 11.2%, 24.5%, and 6.8% at 3 poultry SPFs (PSPFs) and 15.5% and 25.2% at 2 mammal SPFs (MSPFs). Regarding spatial risk factors, the COVID-19 risk levels were 12.1-, 5.2-, and 5.0-fold higher in the refrigeration/ freezing, by-product processing, and carcass cutting areas, respectively, than in the office area. The risk of COVID-19 infection was 2.1 times higher among employees of subcontractors than among employees of contractors. The COVID-19 risk levels were 5.3- and 3.0-fold higher in foreign workers than in native Korean workers in the PSPFs and MSPFs, respectively.Conclusion: As the COVID-19 pandemic continues, a detailed policy for infectious disease prevention and control intervention is needed, without interrupting economic activities. Thus, we propose an ideal intervention plan to prevent COVID-19 through disinfection and preemptive testing and to block its transmission through effective contact management during outbreaks at SPFs.