[Epidemiological characteristics of a 2019-nCoV outbreak caused by Omicron variant BF.7 in Shenzhen].

Objective: To explore the epidemiological characteristic of a COVID-19 outbreak caused by 2019-nCoV Omicron variant BF.7 and other provinces imported in Shenzhen and analyze transmission chains and characteristics. Methods: Field epidemiological survey was conducted to identify the transmission chain, analyze the generation relationship among the cases. The 2019-nCoV nucleic acid positive samples were used for gene sequencing. Results: From 8 to 23 October, 2022, a total of 196 cases of COVID-19 were reported in Shenzhen, all the cases had epidemiological links. In the cases, 100 were men and 96 were women, with a median of age, M (Q1, Q3) was 33(25, 46) years. The outbreak was caused by traverlers initial cases infected with 2019-nCoV who returned to Shenzhen after traveling outside of Guangdong Province.There were four transmission chains, including the transmission in place of residence and neighbourhood, affecting 8 persons, transmission in social activity in the evening on 7 October, affecting 65 persons, transmission in work place on 8 October, affecting 48 persons, and transmission in a building near the work place, affecting 74 persons. The median of the incubation period of the infection, M (Q1, Q3) was 1.44 (1.11, 2.17) days. The incubation period of indoor exposure less than that of the outdoor exposure, M (Q1, Q3) was 1.38 (1.06, 1.84) and 1.95 (1.22, 2.99) days, respcetively (Wald χ2=10.27, P=0.001). With the increase of case generation, the number and probability of gene mutation increased. In the same transmission chain, the proportion of having 1-3 mutation sites was high in the cases in the first generation. Conclusions: The transmission chains were clear in this epidemic. The incubation period of Omicron variant BF.7 infection was shorter, the transmission speed was faster, and the gene mutation rate was higher. It is necessary to conduct prompt response and strict disease control when epidemic occurs.

Real-time Facial Expression Recognition via Dense & Squeeze-and-Excitation Blocks

Due to the coronavirus disease 2019 (COVID-19) pandemic, traditional face-to-face courses have been transformed into online and e-learning courses. Although online courses provide flexible teaching and learning in terms of time and place, teachers cannot be fully aware of their students’ individual learning situation and emotional state. The cognition of learning emotion with facial expression recognition has been a vital issue in recent years. To achieve affective computing, the paper presented a fast recognition model for learning emotions through Dense Squeeze-and-Excitation Networks (DSENet), which rapidly recognizes students’ learning emotions, while the proposed real-time online feedback system notifies teacher instantaneously. Firstly, DSENet is trained and validated by an open dataset called Facial Expression Recognition 2013. Then, we collect students’ learning emotions from e-learning classes and apply transfer learning and data augmentation techniques to improve the testing accuracy. The proposed DSENet model and real-time online feedback system aim to realize effective e-learning for any teaching and learning environments, especially in the COVID-19 environment of late © This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.