Résumé
Objective@#To analyze the epidemiological characteristics and influencing factors of norovirus aggregation in primary and secondary schools in Haidian District of Beijing from 2015 to 2018,and to provide scientific basis for the prevention and control of school aggregation epidemic situation.@*Methods@#An epidemiological method was used to analyze the epidemic characteristics of norovirus aggregation in the primary and secondary schools in Haidian District of Beijing from January 2015 to December 2018. Multivariate Logistic was used to analyze the influencing factors of norovirus aggregation.@*Results@#A total of 74 cases of norovirus aggregation in primary and secondary schools in Haidian District of Beijing from 2015 to 2018 were reported, involving 52 primary and secondary schools. Totally 1 291 suspected cases and a median of 12.5 cases of single epidemic were reported. Winter and spring were high incidence season. There was significant difference in the incidence rate of epidemic situation in primary and secondary schools(χ2=98.82, P<0.01). There was significant difference in the incidence rate between men and women(χ2=55.56, P<0.01). A total of 648 samples and 486 positive samples were collected, with a positive rate of 75.00%, mainly GⅡ virus, accounting for 87.45%. Multivariate Logistic regression showed that the scale of school(>2 000，1 000~2 000), student’s hand hygiene habit,requirement for medical care after the outbreak is the influence factor of the outbreak(OR=3.78，2.95，8.25，2.88).@*Conclusion@#Poor hand hygiene habits are the most important risk factors for the outbreak, so schools and parents should cultivate children to develop good hygiene habits of washing hands before and after meals, and timely isolation of cases found in schools is also an important measure to prevent and control the epidemic.
Résumé
Ras-related C3 botulinum toxin substrate 1 (Rac1), a member of the Rho GTPase family which plays important roles in dendritic spine morphology and plasticity, is a key regulator of cytoskeletal reorganization in dendrites and spines. Here, we investigated whether and how Rac1 modulates synaptic transmission in mouse retinal ganglion cells (RGCs) using selective conditional knockout of Rac1 (Rac1-cKO). Rac1-cKO significantly reduced the frequency of AMPA receptor-mediated miniature excitatory postsynaptic currents, while glycine/GABA receptor-mediated miniature inhibitory postsynaptic currents were not affected. Although the total GluA1 protein level was increased in Rac1-cKO mice, its expression in the membrane component was unchanged. Rac1-cKO did not affect spine-like branch density in single dendrites, but significantly reduced the dendritic complexity, which resulted in a decrease in the total number of dendritic spine-like branches. These results suggest that Rac1 selectively affects excitatory synaptic transmission in RGCs by modulating dendritic complexity.