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ObjectiveTo present the exploration and application of a prospective follow-up research method for acute infectious disease surveillance based on natural community populations， using COVID-19 infection as an example， and to provide a reference for improving the infectious disease surveillance and early warning system. MethodsA multi-stage probability proportional sampling method was employed to sample residents from all communities of 16 administrative districts in Shanghai， with households as the units. A cohort for acute infectious diseases based on natural community populations was established. The baseline survey was conducted for all cohort subjects， and COVID-19 antigen test kits were distributed. From December 21， 2022 to September 30， 2023， prospective follow-up monitoring of COVID-19 antigen and nucleic acid was carried out on the study subjects on a weekly basis. The baseline characteristics and follow-up information of the cohort subjects were described. ResultsThe cohort for acute infectious diseases included a total of 12 881 subjects， comprising 6 098 males （47.3%） and 6 783 females （52.7%）. The baseline survey revealed that 35.2% （4 540/12 881） of the subjects had a history of COVID-19 infection. During the follow-up period from December 21， 2022 to September 30， 2023， the average incidence density in the cohort was 0.61/person-year， with a higher incidence density in females （0.63/person-year） compared to males （0.59/person-year）. Individuals aged 60 and above （0.64/person-year） and those with underlying health conditions （0.67/person-year） had a higher incidence density. Healthcare workers showed a notably higher incidence density （0.84/person-year） than that in other occupational groups. As of September 30， 2023， a total of 340 subjects in the cohort experienced secondary infections， with a median interval of 170 days between the first and second infections. ConclusionThis study applies cohort study method to acute infectious disease surveillance， providing crucial data support for estimating infection rates and forecasting alerts for acute infectious diseases in the community. This method can be promoted and applied as a new approach for acute infectious disease surveillance.
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Objective:Reflux esophagitis (RE) may be negatively correlated with Helicobacter pylori ( H. pylori) infection, but the conclusion and relevant mechanism is still controversial. This study proposed to explore the correlation between RE and H. pylori infection based on natural population. Methods:From July 2013 to December 2014, 3 940 residents aged 40-69 years were recruited in Linqu County of Shandong Province and Hua County of Henan Province by the whole sampling method. All the subjects underwent gastroscopy, and gastric mucosa biopsy specimens were collected for pathological diagnosis and Warthin-Starry (WS) staining to identify H. pylori infection. Venous blood samples of some subjects were collected for H. pylori immunoglobulin G ( H. pylori-IgG) detection. Also, demographic and sociological data were collected. Chi-square test and logistic regression were used to analyze the correlation between RE and H. pylori infection. Results:A total of 359 cases of RE were detected. Excluding RE and other upper gastrointestinal organic diseases, 3 382 cases were considered as controls. Chi-square test showed that WS staining positive rate in RE group was significantly lower than that in control group ( P=0.023), but there was no significant difference in the positive rate of H. pylori-IgG between the two groups ( P=0.281). There were significant differences between RE group and control group in gender composition, age, body mass index (BMI), smoking, alcohol consumption, education level and mucosal active inflammation. Multivariate regression analysis showed that RE was negatively correlated with gastric mucosa active inflammation [ OR=0.754 (95% CI 0.600-0.949), P=0.016], and positively correlated with male [ OR=4.231 (95% CI 3.263-5.486), P<0.001], age ≥60 years, BMI≥24 kg/m 2 [ OR=1.540 (95% CI 1.220-1.945), P<0.001]. Compared to those aged 40-49 years and 50-59 years, the odds ratio ( OR) of RE in these aged ≥60 years were 1.566 (95% CI 1.144-2.143, P=0.005) and 1.405 (95% CI 1.093-1.805, P=0.008). Conclusion:RE is more closely related to H. pylori present infection. Multivariate analysis showed that RE is negatively correlated with active inflammation of gastric mucosa caused by H. pylori infection, and positively correlated with male, overweight and aged ≥60 years.
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In order to evaluate the effect of weed interference and plant density on performance of grain corn, an experiment was carried out as split-plot based on randomized completed bloke design (RCBD) with three replications at the Agriculture Research Station, University of Tabriz, Iran in 2009. Plant density levels including: 5, 7, 10 and 16 plant/m-2 was allocated to the main plots and weed interference at three levels including: weed free (w1), once in a row weed interference (w2) and perfect weed interference (w3) were assigned to subplots. The results showed that weed interference on grain yield, 1000 seed weight kernel weight and number of ear had a significant effect. With increasing of natural weed interference during growth period, grain yield, 1000 seed weight, kernel weight and number of ear decreased. Also, interaction between weed interference and plant density was significant in kernel weight of ear. Between different densities the greatest grain yield with 1020 g/m-2 obtained from 16 plant/m-2 and weed free treatment Weeds in treatments of once in a row weed interference 50 percent and treatments of perfect weed interference in long of growth period 75 percent grain yield decreased. Results showed that with increasing plant density, corn can increase its competitiveness with natural weeds of field increased the grain yield. Generally, the results indicate that the sensitivity to weeds interference especially in low plant density due to the effect of early competitive start may influence extremely the yield of maize.