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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.
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Objective To investigate the molecular characteristics of dengue virus serotype 2 (DENV2) in Guangzhou during 2001-2015,and analyze the E gene of the strains isolated,the phylogenetic tree and molecular clock were constructed to know about the evolution of the strains.Methods The serum samples of the patients were detected by real time PCR,and positive samples were used to isolate dengue virus by using C6/36 cells.The E gene of the isolated strains were sequenced.The phylogenetic tree was constructed by using software Mega 4.0,and the molecular clock was drawn by using software BEASTv1.8.2.Results Twenty-six dengue virus strains were isolated between 2001 and 2015.They were all clustered into 2 genotypes,i.e.cosmopolitan genotype and Asian genotype Ⅰ.The strains isolated in Guangzhou shared high homology with Southeast Asian strains.The cosmopolitan genotype was divided into 2 sub-genotype at about 46 and 35 years ago.The substitution rate of dengue virus serotype 2 in Guangzhou was 7.1 × 10-4 per year per site.Conclusions There were close relationship between the Guangzhou strains and Southeast Asian strains.Guangzhou was at high risk of imported dengue fever,outbreak of dengue hemorrhagic fever and dengue shock syndrome.There might be two ways of introduction of cosmopolitan genotype.The substitution rate of the strains in Guangzhou was similar to that in the neighbor countries.
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Objective To evaluate the efficacy of a sustained releasing mosquito larvicide package against larval breeding and its impact on water and plant,in order to provide a scientific evidence for its application in control and prevention of Dengue.Methods Guangzhou Center for Disease Control and Prevention was chosen as the test place.Twenty test sites were set up,2 bags of sustained releasing larvicides package,1 bag of sustained releasing larvicides package,3 g 1％ temephos granules and nothing were put into 4 glass bottles for each test site from July to December in 2014,respectively.The 4 glass bottles were called high dose (H) group,low dose (L)group,positive control (P) group and blank control (B) group,respectively.The 4 groups were observed at intervals of 10 days for 19 times.Environmental air temperature,turbidity of water,number of larvae and damage of plant were recorded.And 5 test sites were selected to collect water specimen.The chemical oxygen demand,ammonia nitrogen concentration and temephos concentration of water specimen were detected.Results The larval breeding rates were 0 (0/380),1.1％ (4/380),0.8％ (3/380) and 63.4％ (241/380),damage rates of plant were 5.0％ (19/380),5.5％ (21/380),4.7％ (18/380),4.7％ (18/380) and turbidty rates of water were 24.5％ (93/380),19.7％ (75/380),33.4％ (127/380) and 20.3％ (77/380) in H,L,P and B groups,respectively.Statistically significant differences were seen in larval breeding rate and turbidity rate of water between different groups (x2 =823.565,24.715,all P ＜ 0.05),but they were not seen in damage rate of plant (x2 =0.332,P ＞ 0.05).The temephos concentrations were 1.24,0.78 and 2.33 mg/L in H,L and P groups,respectively.Statistically significant differences were seen in temephos concentration between different groups (H =35.426,P ＜ 0.01),but they were not seen in chemical oxygen demand and ammonia nitrogen concentration (H =0.239,0.013,all P ＞ 0.05).Conclusions The sustained releasing package of mosquito larvicide makes less pollution to water and has no impact on water turbidity.Moreover,it doesn't damage the aquatic plant.The efficacy of the sustained releasing package of mosquito larvicide could effectively prevent mosquito larval breeding in Dengue epidemic period.
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Objective To investigate the molecular characteristics of dengue virus serotype 2 (DENV2) in Guangzhou during 2001-2015,and analyze the E gene of the strains isolated,the phylogenetic tree and molecular clock were constructed to know about the evolution of the strains.Methods The serum samples of the patients were detected by real time PCR,and positive samples were used to isolate dengue virus by using C6/36 cells.The E gene of the isolated strains were sequenced.The phylogenetic tree was constructed by using software Mega 4.0,and the molecular clock was drawn by using software BEASTv1.8.2.Results Twenty-six dengue virus strains were isolated between 2001 and 2015.They were all clustered into 2 genotypes,i.e.cosmopolitan genotype and Asian genotype Ⅰ.The strains isolated in Guangzhou shared high homology with Southeast Asian strains.The cosmopolitan genotype was divided into 2 sub-genotype at about 46 and 35 years ago.The substitution rate of dengue virus serotype 2 in Guangzhou was 7.1 × 10-4 per year per site.Conclusions There were close relationship between the Guangzhou strains and Southeast Asian strains.Guangzhou was at high risk of imported dengue fever,outbreak of dengue hemorrhagic fever and dengue shock syndrome.There might be two ways of introduction of cosmopolitan genotype.The substitution rate of the strains in Guangzhou was similar to that in the neighbor countries.
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<p><b>OBJECTIVE</b>To understand the threshold of Breteau Index (BI) on Dengue fever outbreak in Guangzhou.</p><p><b>METHODS</b>Dengue cases from Guangzhou during 2006 to 2012 in the National Infectious Disease Report and Management System were collected and described. Receiver-operating characteristic (ROC) curve was used to judge the threshold of BI on the outbreaks of Dengue fever.</p><p><b>RESULTS</b>A total of 1 038 local cases were reported from 2006 to 2012 in Guangzhou city, with a total of 71 outbreaks and 259 sporadic episodes. Data from the ROC curve analysis showed that the highest Youden index that BI predicting Dengue fever outbreaks or sporadic were 6.4 and 9.5, respectively. When using BI = 6.4 in predicting the sporadic case of Dengue, sensitivity and specificity were 67.8% , 79.1% , respectively. When using BI = 9.5 in predicting the outbreaks of Dengue, sensitivity and specificity were 81.7%, 90.9%, respectively.</p><p><b>CONCLUSION</b>Both BI = 5.0 and BI = 9.5 showed effects on predicting the nature of sporadic or outbreak on Dengue, suggesting that the threshold need to be monitored, according to the purpose of control and availability of manpower, in order to get better sensitivity and specificity.</p>