ABSTRACT
Objectives: Site-specific wastewater surveillance could potentially control COVID-19 outbreaks more effectively at long-term care facilities (LTCF). It could identify the presence of pre-symptomatic and asymptomatic COVID-19 infections in the facility and therefore initiate timely outbreak control measures. Besides, compared to repetitive screenings of residents and staff using diagnostic tests, screenings based on positive wastewater test results incur fewer costs and less discomfort. We evaluated the effectiveness of LTCF-site-specific wastewater surveillance in preventing COVID-19 outbreaks, by comparing the scenario where more diagnostic tests were initiated due to positive wastewater test results and the base case of no action. Method(s): We built a susceptible-infected-cases-recovered model to study COVID-19 transmission at LTCF under the base-case and wastewater surveillance scenario. We used data from an outbreak during the Omicron wave in one LTCF in Edmonton, Canada (December 2021 - March 2022), where wastewater data did not initiate actions. We fit base-case model parameters with daily cases and testing data using the nonlinear least-squares method. We hypothesized 10%-50% more diagnostic tests in the wastewater scenario. We compared the outbreak size, i.e., predicted numbers of infections, to measure the effectiveness. We used the Mann-Whitney U test to identify whether the outbreak size in the wastewater scenario was significantly smaller. Result(s): Results reported are subject to minor changes as modelling work is ongoing. The number of infections peaked on day 25 in the base case, with 23.8% of individuals being infected. In the wastewater scenario, all hypothesized values resulted in a significantly smaller outbreak size;only 10% more diagnostic tests could lead to 5.4% fewer infections (p=0.03) at the peak. Conclusion(s): This pilot study demonstrates the potential effectiveness of LTCF-site-specific wastewater surveillance to prevent COVID-19 outbreaks. Future works include engaging policymakers in analyzing specific wastewater-based actions and estimating the costs of controlling COVID-19 to explore the cost-effectiveness of wastewater surveillance.Copyright © 2023
ABSTRACT
In recent years, on-site visitation has been strictly restricted in many scenic areas due to the global spread of the COVID-19 pandemic. "Cloud tourism”, also called online travel, uses high-resolution photographs taken by unmanned aerial vehicles (UAVs) as the dominant data source and has attracted much attention. Due to the differences between ground and aerial observation perspectives, the landscape elements that affect the beauty of colored-leaved forests are quite different. In this paper, Qixia National Forest Park in Nanjing, China, was chosen as the case study area, and the best viewpoints were selected by combining tourists' preferred viewing routes with a field survey, followed by a scenic beauty evaluation (SBE) of the forests with autumn-colored leaves in 2021 from the aerial and ground perspectives. The results show that (1) the best viewpoints can be obtained through the spatial overlay of five landscape factors: elevation, surface runoff, slope, aspect, and distance from the road;(2) the dominant factors influencing the beauty of colored-leaved forests from the aerial perspective are terrain changes, forest coverage, landscape composition, landscape contrast, the condition of the human landscape, and recreation frequency;and (3) the beauty of the ground perspective of the colored-leaved forests is strongly influenced by the average diameter at breast height (DBH), the dominant color of the leaves, the ratio of the colored-leaved tree species, the canopy width, and the fallen leaf coverage. The research results can provide scientific reference for the creation of management measures for forests with autumn-colored leaves. © 2023 by the authors.
ABSTRACT
In this paper, we formulate and analyze a class of discrete state-structured epidemic models that spread through both horizontal and vertical transmissions on networks, where infected individuals can move from one infected state to any other state so that our models include all possible state-transfers (disease deterioration and amelioration) among different states. Many epidemic transmissions with or without vertical transmission in nature can be analyzed by referring to our models, such as HIV-1, viral hepatitis, and Covid-19. We derive the basic reproduction number R0= Rh+ Rv, and prove that the global dynamics are completely determined by the basic reproduction number: if R0 ≤ 1, the disease-free equilibrium is globally asymptotically stable and the disease always dies out;if R0 > 1, the disease-free equilibrium is unstable, and there exists a unique endemic equilibrium that is globally asymptotically stable, and the disease persists at a positive level in the population. It also implies that vertical transmission has an impact on maintaining infectious diseases when horizontal transmission cannot sustain the disease on its own. The proof of global stability is based on the graph-theoretic approach and answer the open problem left in [1]. Finally, numerical simulations are performed to illustrate the theoretical results. © 2023 American Institute of Mathematical Sciences. All rights reserved.
ABSTRACT
In this paper, we formulate and analyze a class of discrete state structured epidemic models that spread through both horizontal and vertical transmissions on networks, where infected individuals can move from one infected state to any other state so that our models include all possible state transfers (disease deterioration and amelioration) among different states. Many epidemic transmissions with or without vertical transmission in nature can be analyzed by referring to our models, such as HIV-1, viral hepatitis, and Covid19. We derive the basic reproduction number R0= Rh+ Rv, and prove that the global dynamics are completely determined by the basic reproduction number: if R0 <= 1, the disease-free equilibrium is globally asymptotically stable and the disease always dies out;if R0 > 1, the disease-free equilibrium is unstable, and there exists a unique endemic equilibrium that is globally asymptotically stable, and the disease persists at a positive level in the population. It also implies that vertical transmission has an impact on maintaining infectious diseases when horizontal transmission cannot sustain the disease on its own. The proof of global stability is based on the graph-theoretic approach and answer the open problem left in [1]. Finally, numerical simulations are performed to illustrate the theoretical results.
ABSTRACT
Objective: To understand the epidemiological characteristics of a local clustered epidemic caused by 2019-nCoV Delta variant in Ningbo and provide reference for the improvement of COVID-19 epidemic prevention and control. Methods: Case finding was conducted based on case definitions, and field epidemiological investigation of COVID-19 cases was carried out. In which Nasal and oropharyngeal swabs of the cases were collected for pathogen testing, and the results were analyzed with descriptive epidemiological methods. Results: A total of 74 COVID-19 cases were reported in this epidemic, and the cases were mainly mild ones, accounting for 87.84% (65/74), and there were no severe or critical cases. The epidemic curve showed a human-to-human transmission mode, indicating that a transmission for at least six generations had occurred. The age of the COVID-19 patients ranged from 2 years to 80 years, and 27.03% (20/74) of the cases were older than 60 years. The cases were mainly workers (55.41%, 41/74) and housework/the unemployed (27.03%, 20/74). The COVID-19 epidemic was limited, and no further spread to other areas occurred. The transmission chain among the cases was clear, and the gene sequencing results confirmed that the current epidemic was caused by 2019-nCoV Delta variant, which was highly homologous to the strains from other province. Conclusion: The local COVID-19 epidemic in Ningbo was caused by imported cases of COVID-19 from other province, and local community spread occurred through daily contacts between cases and contacts.
Subject(s)
COVID-19 , Epidemics , COVID-19/epidemiology , Child, Preschool , Data Collection , Humans , SARS-CoV-2ABSTRACT
The first case of Corona Virus Disease 2019 (COVID-19) was reported in Wuhan, China in December 2019. Since then, COVID-19 has quickly spread out to all provinces in China and over 150 countries or territories in the world. With the first level response to public health emergencies (FLRPHE) launched over the country, the outbreak of COVID-19 in China is achieving under control in China. We develop a mathematical model based on the epidemiology of COVID-19, incorporating the isolation of healthy people, confirmed cases and contact tracing measures. We calculate the basic reproduction numbers 2.5 in China (excluding Hubei province) and 2.9 in Hubei province with the initial time on January 30 which shows the severe infectivity of COVID-19, and verify that the current isolation method effectively contains the transmission of COVID-19. Under the isolation of healthy people, confirmed cases and contact tracing measures, we find a noteworthy phenomenon that is the second epidemic of COVID-19 and estimate the peak time and value and the cumulative number of cases. Simulations show that the contact tracing measures can efficiently contain the transmission of the second epidemic of COVID-19. With the isolation of all susceptible people or all infectious people or both, there is no second epidemic of COVID-19. Furthermore, resumption of work and study can increase the transmission risk of the second epidemic of COVID-19.
ABSTRACT
We examine a period in which the in-principle prohibition of share repurchases was relaxed in 2018 to allow for the repurchase of shares whose prices dropped materially or were below book value. We find that share-loan pledges by controlling shareholders are significantly and positively associated with share repurchases for a sample of 3,531 Chinese firms. This finding is robust using entropy and propensity score matched samples, 2SLS IV regressions, regression discontinuity design (RDD), and two exogenous shocks (the China-US trade war in 2018 and the COVID-19 pandemic in 2020). The association remains robust but becomes less strong with state ownership and with above industry average firm agency problems, leverage ratios and financial constraints/distress (i.e., other share repurchase motives). Our findings highlight the importance of financial market regulations on share-loan pledging and share repurchases in emerging markets during periods of heightened firm-specific and systemic margin call risk and impending liquidation of share-loan pledges.
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When there is a shortage of ventilators in a hospital, an anesthesia machine can be used as a ventilator. However, using an anesthesia machine as a ventilator requires that it be set up in a way that would not be familiar to medical personnel who normally work with ventilators. To teach medical staff how to do this, we developed a smartphone augmented reality app that allows a user to interact with a life-size virtual anesthesia machine, and leads them through the necessary steps. This makes it possible for the user to practice the setup procedures in a way that preserves the 3D spatial layout of the tasks without requiring access to the physical machine.
ABSTRACT
Hepatitis C infection is a serious public health threat, and the World Health Organization has recommended the elimination of public health threats from viral hepatitis, including hepatitis C, by 2030. Many countries and regions are actively exploring strategies and models to eliminate the public health threat of hepatitis C. It is estimated that there are at least 7.6 million cases of chronic hepatitis C in China, with both diagnosis and treatment rates far away to 2030 target. China's government, social organizations and doctors at different levels are also actively exploring the mode of eliminating the public health threat of hepatitis C in China, including the main mode supported by national standards, government-led mode, social institution undertaking and government-supported mode, medical alliance mode, screening in high-prevalence areas and services contracted with family doctors. China can have a lessons learning from international and ourselves experience, particularly as "Test and treat all based on needs and demand" strategy in Covid-19 control, finally achieve eliminate the public health threat of hepatitis C as soon as possible.