Objective To analyze the current status and influencing factors of occupational stress among medical staff during major public health emergencies. Methods A total of 491 medical staff in Guangzhou City was selected as the research subjects using a convenient sampling method. The Job Content Questionnaire and Effort-Reward Imbalance Questionnaire were used to evaluate the occupational stress level in the job demand-control (JDC) and effort-reward imbalance (ERI) models among the staff. Results Among the research subjects, the detection rates of occupational stress in JDC and ERI models were 50.1% and 52.5%, respectively. There was no significant difference in the detection rates of occupational stress between the two models (P>0.05). The result of multivariate logistic regression analysis showed that individuals with lower monthly income and longer weekly working hours had a higher risk of occupational stress in both JDC and ERI models (all P<0.05). Staff with night shift, daily sleep time less than six hours, and dissatisfaction with the protective measures provided by the hospital had higher risk of occupational stress than those with no night shift, daily sleep time at least six hours, and satisfaction with the protective measures provided by the work place in JDC and ERI models (all P<0.01). The risk of ERI model occupational stress of personnel who had been exposed to COVID-19 cases or suspected cases was higher than that in those who had not been exposed (P<0.05). Conclusion Medical staff experience a certain level of occupational stress, characterized by both JDC and ERI models, during major public health emergencies. The main influencing factors included personal monthly income, weekly working hours, night shift, sleep time, satisfaction with protective measures and occupational exposure.

Objective:To isolate and identify SARS-CoV-2 epidemic strains and analyze the sequence characteristics of the virus strains following serial passages.Methods:Eleven nasopharyngeal swabs positive for SARS-CoV-2 antigen were collected from December 2022. Quantitative real-time PCR was used to detect SARS-CoV-2 nucleic acid, and positive specimens were inoculated onto Vero cells for virus isolation. The isolated strains were identified by Western blot and indirect immunofluorescence assay. The morphology of the isolated strains was observed using transmission electron microscopy. Nucleic acid was extracted from the isolates and passaged viruses for further sequencing and analysis.Results:All 11 specimens tested positive for SARS-CoV-2 using quantitative real-time PCR. SARS-CoV-2 strains were successfully isolated from seven specimens, and could be adaptively cultured, passaged, and expanded on Vero cells, achieving a peak titer exceeding 10 6.25 50% cell culture infectious dose (CCID 50)/ml. Western blot and indirect immunofluorescence results showed that the isolates could be specifically recognized by monoclonal antibodies and convalescent serum against SARS-CoV-2. Transmission electron microscopy revealed oval-shaped viral particles with diameters of approximately 100 nm. Next-generation sequencing of the viral isolates demonstrated a sequence homology greater than 99.50% with the Wuhan-Hu-1 reference strain (NC_045512) and 99.98% among the seven isolated strains, and all of the isolates belonged to the Omicron BF.7 variant. Sequence analysis after continuous passage and plaque purification of the BJ-NVSI-20230005 isolate showed that compared with passages 1-3, passages 4-6 had one nucleotide site mutation (C→T) in the ORF1ab gene and a deletion of 3 bp in the E gene, which resulted in a change from leucine to phenylalanine and the deletion of valine, respectively. Polymorphisms were observed in the sequences of plaque-purified clones. Conclusions:The seven successfully isolated SARS-CoV-2 strains all belong to the SARS-CoV-2 BF.7 variant, which is consistent with the prevalence trend in mainland China in December 2022.