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Objective: To analyze the course of disease and epidemiological parameters of COVID-19 and provide evidence for making prevention and control strategies. Methods: To display the distribution of course of disease of the infectors who had close contacts with COVID-19 cases from January 1 to March 15, 2020 in Guangdong Provincial, the models of Lognormal, Weibull and gamma distribution were applied. A descriptive analysis was conducted on the basic characteristics and epidemiological parameters of course of disease. Results: In total, 515 of 11 580 close contacts were infected, with an attack rate about 4.4%, including 449 confirmed cases and 66 asymptomatic cases. Lognormal distribution was fitting best for latent period, incubation period, pre-symptomatic infection period of confirmed cases and infection period of asymptomatic cases; Gamma distribution was fitting best for infectious period and clinical symptom period of confirmed cases; Weibull distribution was fitting best for latent period of asymptomatic cases. The latent period, incubation period, pre-symptomatic infection period, infectious period and clinical symptoms period of confirmed cases were 4.50 (95%CI:3.86-5.13) days, 5.12 (95%CI:4.63-5.62) days, 0.87 (95%CI:0.67-1.07) days, 11.89 (95%CI:9.81-13.98) days and 22.00 (95%CI:21.24-22.77) days, respectively. The latent period and infectious period of asymptomatic cases were 8.88 (95%CI:6.89-10.86) days and 6.18 (95%CI:1.89-10.47) days, respectively. Conclusion: The estimated course of COVID-19 and related epidemiological parameters are similar to the existing data.
Assuntos
Humanos , COVID-19 , Estudos de Coortes , Busca de Comunicante , Incidência , Estudos ProspectivosRESUMO
Objective To assess the effectiveness of prevention program on iodine deficiency disorders and iodine nutritional status of residents in Guangdong Province.Methods Probability proportionate to size sampling(PPS) was employed in surveillance of iodine deficiency disorders.Thirty counties(cities,districts) were selected in Guangdong Province.In each county(city,district) one township(street) was selected; in each township (street) one primary school was selected and in each primary school 40 children aged 8-10 were chosen to examine their thyroid and to collect salt samples at their home for determination of salt iodine.Out of the 40 children,12 children were chosen to collect urine samples for determination of urinary iodine.From the primary schools chosen,40 grade 5 students were selected for intelligence quotient(IQ) test.In the nearby of the primary schools,3 townships(towns,street) were selected and in each township(town,street) 5 pregnant and 5 lactating women were selected to collect their urine samples for determination of urinary iodine.Type-B ultrasonic was used in measuring the thyroid volume.The iodine content of urine samples was measured by the method of arsenic and cerium catalysis spectrophotometry.The iodine content of salt was determined quantitatively with the titration method.IQ was tested by Chinese combined Raven's test.According to geographical location and the implementation of iodized salt,the effects of iodized salt on iodine deficiency disorders were analyzed in the plains and the Pearl River Delta Coastal region with mild iodine deficiency(iodized salt implementation region,referred to as the plains and the PRD),historical iodine deficiency areas (iodized implementation region) and the eastern and the western coastal areas of Guangdong(areas with non-iodized salt problem,referred to as the eastern and the western Guangdong).Results A total of 1200 children aged 8 to 10 were examined by type-B ultrasonic test,and goiter rate was 3.5％ (42/1200).The differences of goiter rate between the plains and the PRD,the historical iodine deficiency areas and the eastern and the western Guangdong were statistically significant (x2 =6.6,P ＜ 0.05).The goiter rate (6.1％) in the eastern and the western Guangdong was significantly higher than that of the plains and the PRD and the historical iodine deficiency areas (3.3％,2.0％,x2 =5.6,7.1,all P ＜ 0.05).A total of 1200 salt samples were examined.The median and coefficient of variation of iodine in the salt were 31.0 mg/kg and 23.2％,respectively.Coverage of iodized salt was 97.5％(1170/1200) while 96.1％(1153/1200) of consumed iodized salt was qualified.The median urinary iodine of 1200 children aged 8-10 was 186.5 μg/L,and the differences of median urinary iodine between the plains and the PRD,the historical iodine deficiency areas and the eastern and the western Guangdong were statistically significant(x2 =5.9,P ＜ 0.05).The median urinary iodine of the eastern and the western Guangdong(162.4 μg/L) was significantly lower than that of the plains and the PRD(207.5 μg/L,x2 =8.7,P ＜ 0.01).The difference of median urinary iodine between the plains and the PRD,the historical iodine deficiency areas and the eastern and the western Guangdong was statistically significant(x2 =58.9,P＜ 0.01).The median urinary iodine of the eastern and the western Guangdong(109.6 μg/L) was significantly lower than that of the historical iodine deficiency areas and the plains and the PRD(152.9,155.2 μg/L,x2 =18.3,20.6,all P ＜ 0.05).The mean IQ of the 1208 grade 5 students was 102.8 ± 14.3.The IQ of the plains and the PRD(104.3 ± 13.9) and the historical iodine deficiency areas(102.7 ± 14.3) was significantly higher than that of the eastern and the western Guangdong(100.3 ± 14.7,t =3.8,2.1,P＜ 0.01 orP＜ 0.05).Conclusions The goal of iodine deficiency disorders elimination is achieved as scheduled in Guangdong Province.The health level of general population has been improved significantly.Iodine nutrition is in the appropriate range (100-199 μg/L) in general population but low in pregnant women.The selling of non-iodized salt in the eastern and the western Guangdong Province should be followed closely.
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<p><b>OBJECTIVE</b>To establish a model for predicting the density of Aedes albopictus based on the climate factors.</p><p><b>METHODS</b>The data of Aedes albopictus density and climate changes from 1995 to 2001 in Guangzhou were collected and analyzed. The predicting model for Aedes albopictus density was established using the Artificial Neural Network Toolbox of Matlab 7.0 software package. The climate factors used to establish the model included the average monthly pressure, evaporation capacity, relative humidity, sunshine hour, temperature, wind speed, and precipitation, and the established model was tested and verified.</p><p><b>RESULTS</b>The BP network model was established according to data of mosquito density and climate factors. After training the neural network for 25 times, the error of performance decreased from 0.305 539 to 2.937 51x10(-14). Verification of the model with the data of mosquito density showed a concordance rate of prediction of 80%.</p><p><b>CONCLUSION</b>The neural network model based on the climate factors is effective for predicting Aedes albopictus density.</p>