Objective:To analyze the epidemiological characteristics of novel coronavirus positive cases including confirmed cases with clinical symptoms and asymptomatic infected cases in Guangzhou.Methods:Epidemiological data were collected on the nucleic acid positive cases of COVID-19 in Guangzhou from January to September 2020. The epidemiological characteristics, the distribution of time intervals between the confirmed/isolation date and the date of the first positive detection were analyzed, at last the influencing factors for the confirmed cases and asymptomatic infected persons were discussed.Results:From January 7 to September 4 in 2020, a total of 1 097 nucleic acid positive cases were identified, including 658 confirmed cases (59.98%) and 439 asymptomatic infected cases (40.02%). Among the 658 confirmed cases, the median age was 42 years old, the cases indicated two significant peaks. one of the peaks was related to the imported and associated cases from Hubei province, and the other peak was connected with individuals from overseas. In terms of 439 asymptomatic infected cases, the median age was 32 years old. There were two stages in these cases. The first stage followed the second peak of confirmed cases, and the second stage overlapped with the confirmed cases in Guangzhou when the epidemic was in a period of normal prevention and control, mainly related to imported cases from abroad. The asymptomatic infected persons accounted for 57.32% in all the imported infected cases. In both of asymptomatic and symptomatic cases, the positive rate of pharyngeal swabs was higher than that of nasopharyngeal swabs and anal swabs. There were statistically significant differences in age, source of infection and gender composition between confirmed cases and asymptomatic infected persons ( P<0.05). Older age groups were more likely to have clinical symptoms, with ≥40 years being the risk factor for confirmed cases (OR=2.334, P=0.001), and 20-39 years less likely to have clinical symptoms (OR=0.620, P=0.047), compared with the 0-19 years old group. Compared with those infected in China, those infected abroad were less likely to develop clinical symptoms and became confirmed cases (OR=0.723, P=0.013). Women were more likely to have clinical symptoms than men (OR=1.574, P=0.001). Conclusions:At present, asymptomatic infected persons and confirmed patients with clinical symptoms co-existed, and the number of asymptomatic infected patients was higher than that of confirmed cases in Guangzhou. High age, domestic infection and female may be risk factors for confirmed cases. It was of great value to further explore these underlying mechanisms for the prevention and treatment of the COVID-19.

Objective:To explore any effect of transcranial direct current stimulation (tDCS) on neurons, behavior, cerebral blood flow (CBF), vascular regeneration, and the expression of vascular endothelial growth factor (VEGF) and CD34 protein in rats modeling cerebral infarction.Methods:Thirty-two adult male Sprague-Dawley rats were randomly divided into a sham surgery group (Sham group), a model group (modeled with middle cerebral artery occlusion, MCAO group), an anode transcranial direct current stimulation group (A-tDCS group), and a cathode transcranial direct current stimulation group (C-tDCS group), each of 8. MCAO models were established in the rats of the MCAO, A-tDCS and C-tDCS groups using thread fixation. Twenty-four hours after successful modeling, both the Sham and MCAO groups were connected with electrodes without current stimulation, while the A-tDCS and C-tDCS groups were given 20 minutes of 200μA anodic or cathodic electrical stimulation daily, 5 days a week for 12 days. Before and 24 hours after the modeling, and then after the 12 days of treatment, the four groups received Longa neurobehavioral scoring. Moreover, three days after the modeling as well as after the 12 days of treatment, changes in CBF were observed using MRI. Any blood vessel regeneration was observed using immunofluorescence methods, and the expression of VEGF and CD34 proteins were detected using western blotting.Results:The rats in the MCAO, A-tDCS and C-tDCS groups exhibited various degrees of neurological deficit after the modeling. After the 12 days of treatment the average neurobehavioral scores of the A-tDCS and C-tDCS groups were significantly lower than that of the MCAO group, with the A-tDCS group′s average significantly lower than that of the C-tDCS group. Three days after the modeling, 3D-arterial spin labeling scanning showed a significant decrease in CBF around the ischemic lesion in the MCAO, A-tDCS and C-tDCS groups, but that had increased to varying degrees after 12 days of treatment. The changes in the A-tDCS and C-tDCS groups were significantly larger than in the MCAO group on average, with the former group improving significantly more than the latter. After the 12 days of treatment, new vascularization and the expression of VEGF and CD34 proteins were significantly higher in the A-tDCS and C-tDCS groups than in the MCAO group, with the change in the former group again significantly greater than in the latter.Conclusions:tDCS can relieve the symptoms of neurological deficits in rats with cerebral infarction, promote vascular regeneration, CBF, and expression of VEGF and CD34 proteins. Anodic is superior to cathodic stimulation.