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Background: As of February 21, 2021, 86,992 cases of coronavirus disease 2019 (COVID-19) were confirmed in the Republic of Korea, with 1,557 deaths and 85,435 cases discharged from isolation. This study investigated the infectivity of individuals with COVID-19 who were retested and found to be severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA-positive after recovering from their primary illness. Methods: We investigated 295 individuals with recurrent SARS-CoV-2 positive results, and 836 of their close contacts. We attempted virus isolation in 108 individuals with recurrent SARS-CoV-2 positivity using cell culture and confirmed the presence of neutralizing antibodies by means of serological tests. Findings: The average age was 45·2 years (range, 1–95 years) and 64% were female. At the time of retesting, 55·6% were asymptomatic, and symptoms included cough (18·0%), expectoration (11·2%), sore throat (10·8%), and fever (9·2%). The reasons for retesting were screening (46%), persistent symptoms (37·6%), and new contact with a confirmed COVID-19 case (9·5%). Virus isolation was attempted in 108 individuals with recurrent SARS-CoV-2 positivity, and all tested negative. Three new cases were identified among household contacts based on SARS-CoV-2 polymerase chain reaction testing. 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. Interpretation: There was no laboratory evidence of viral shedding and no epidemiological evidence of transmission among individuals with recurrent positivity. Funding Statement: This study was funded by the Korea Disease Control and Prevention Agency (No. 4800-4837-301). Declaration of Interests: The authors declare no conflicts of interest related to the study. Ethics Approval Statement: The study was approved by the KDCA Institutional Review Board (2020-03-01-P-A). The board waived the requirement for written informed consent.

The resistive switching characteristics of MnO and CeO2 layers with a large resistance ratio (> 105) were demonstrated. The Ag/MnO/CeO2/Pt devices with heterostructures were fabricated. The bipolar resistive switching behaviors were caused by the formation and disruption of conducting filaments in the switching layers. In CeO2 layer, the formation and rupture of conducting filaments was attributed to the reduction-oxidation reaction of CeO2 and CeO2 − x. The conduction mechanisms of ohmic conduction and Schottky emission had been investigated for resistance switching mechanism.

Outbreaks of avian influenza virus H5N8 first occurred in 2014, and spread to poultry farms in Korea. Although there was no report of human infection by this subtype, it has the potential to threaten human public health. Therefore, we evaluated the pathogenesis of H5N8 viruses in ferrets. Two representative Korean H5N8 strains did not induce mortality and significant respiratory signs after an intranasal challenge in ferrets. However, ferrets intratracheally infected with A/broiler duck/Korea/Buan2/2014 virus showed dose-dependent mortality. Although the Korean H5N8 strains were classified as the HPAI virus, possessing multiple basic amino acids in the cleavage site of the hemagglutinin sequence, they did not produce pathogenesis in ferrets challenged intranasally, similar to the natural infection route. These results could be useful for public health by providing the pathogenic characterization of H5N8 viruses.

s / Journal of Clinical Virology 70 (2015) S1–S126 S39 the samples were tested either by electron microscopy (EM) or norovirus PCR depending on the patient demographics. Since June 2014, all samples regardless of age have been tested for norovirus, rotavirus, sapovirus, astrovirus and enteric adenovirus by real-time PCR. We present the results of the first years testing using the PCR method across all age groups. In addition to the front line PCR a rotavirus genotyping service will also be introduced at the NVRL. Following the recent successful introduction of national vaccination programmes in many European countries, vaccination is likely to be included in the national infant immunisation schedule in Ireland in the near future. The genotyping data will determine the current circulating strains and will also monitor the genetic evolution post implementation of vaccination. Methods: An in-house real time PCR was developed and validated to detect the five main viral causes of gastroenteritis. A reliance on automation has led to a lean streamlined processwhich can test up to approximately 100 samples per day. The genotyping method was a WHO recommended method involving PCR of the VP7 and VP4 regions and gel analysis to determine the G and P genotype. This testing method will be supplemented by Sanger sequencing. Results: The PCR data collated over one year will be presented; thiswill show the seasonal trends of the five viruses across the year and also the prevalence in different age groups. Preliminary data of the circulating strains of rotavirus will also be presented. Conclusion: The introduction of the molecular detection of the main viruses causing gastroenteritis has resulted in a significant increase in the detection of viruses detected when compared with EM. As expected the predominant virus was norovirus in both adults and children. The next prevalent virus was rotavirus which mainly affects children but was also detected in adults to a lesser extent. Sapovirus and astrovirusweremorewidespread than anticipated and finally the enteric adenovirus was the least common virus. http://dx.doi.org/10.1016/j.jcv.2015.07.094